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THE 



MANAGEMENT OF STEEL. 



BY 
J 

GEORGE^EDE ; 

EMPLOYED AT THE ROTAL GUN FACTORIES' DEPARTMENT, WOOLWICH 

ARSENAL. 



jFrem jFourtf; E&ition, JUfeett anH 2Enlavsrtr. 

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186? 

'** of Wash'v^ 
f NEW YORK: 

D. APPLETON & €0., 443 and 445 BROADWAY, 

1867. 






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PREFACE. 



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It lias long been acknowledged that a small 
practical work upon the forging, annealing, hard- 
ening, and tempering of steel, and the case-harden- 
ing of iron, etc., was wanting amongst us ; and it 
was with the object of assisting to supply this 
want, that I contributed my mite in publishing 
and giving my experience in the small work on the 
Management of Steel. How far my efforts have 
succeeded in supplying this want, I am not about 
to say ; but the flattering reception and high praise 
it has received in passing through three editions, 
has induced me to issue a much larger work in a 
revised form. I gave it the title of " The Man- 
agement of Steel " when I published the first edi- 
tion, simply because I could think of no other 
better ; and I continue the name because I am still 
unable to think of one more suitable. In this 
present attempt, my aim has been to write a work 
which would be found as useful to the novice or 



4 PEEFACE. 

amateur mechanic as to the practical man ; and I 
have endeavored to word the subject in such a 
honiely style, that persons totally unacquainted 
with the processes on which it treats will be able 
to judge for themselves as to the reasonableness of 
my remarks. It treats upon the manufacture of 
iron and steel, the choosing of steel for tools, for- 
ging iron and steel, annealing cast iron and steel, 
hardening and tempering of cast iron and steel, 
expansion and contraction of steel, shrinking of 
iron and steel, and the case-hardening of wrought 
iron, also the toughening of mild cast steel for 
guns, shot, railway bars, etc. 

It will, I believe, be found in the future an ines- 
timable treasure to those young mechanics who 
may possess it ; for, in my opinion, if young ap- 
prentices were taught to make themselves better 
acquainted with the materials they work upon, like- 
wise the materials from which their tools are made, 
and the management of that material, the advance- 
ment of the sciences would be greatly hastened, as 
this knowledge would increase the powers of the 
head to contrive, and the powers of the hands to 
execute. The inventions which become publicly 
known are few in comparison with those which 
spring up in the minds of ingenious mechanics 
;u id perish with the hour that gave them birth, 
through the want of a better knowledge of the 



PREFACE. 5 

properties of materials. Although, this work is not 
calculated to supply all this knowledge, still my 
aim has been to be of use, and to contribute toward 
it. I cannot expect that it will entirely satisfy the 
wishes of all my readers; but I have dwelt at 
greater length on those subjects which I have con- 
sidered from my own experience to be the most 
important, and I sincerely hope that its contents 
may prove of some benefit to those who may favor 
me by an impartial perusal. 

George Ede. 
1 Raglan Road. Plumstead. 



CONTENTS. 



CHAPTER I. 

MANUFACTURE OF IRON. 

PAGE 

Wide diffusion of iron — State in which found — Not of a noxious 
nature— Specific gravity — Properties of wrought iron— Used 
for mechanical purposes in three states — Difference of iron 
in the three states 1 1 

Extracting the ores— Roasting— Smelting— Different qualities 

of pig iron used for different purposes 16 

Refining — Puddling — Rolling into bars. 19 

Qualities of wrought iron— Effects of sulphur on hot iron 23 



CHAPTER II. 

MANUFACTURE OF STEEL. 

Steel— How formed— Principle of Mr. Bessemer's process- 
Converting iron into steel by cementation— Change in the 
properties of iron by the penetration of carbon 25 

Mode of prepariug tilted, spring, shear, and cast steel 31 



8 CONTENlb. 

CHAPTER HI. 

• CHOOSING OF STEEL. 

PAGE 

Methods of testing the true quality of tool steel — Not necessary 

to subject it to chemical analysis 34 

Appearance of tool steel on fracture in a hard and soft state — 

Use of aquafortis to distinguish iron from steel 39 



CHAPTER TV. 

FORGING AND WELDING IKON AND STEEL. 

The forge — Welding — Degrees of heat — How distinguished... . 41 

Fuel for forging iron and steel 42 

Heavy iron forgings, how made up — Remarks on the mingling 

of the fibres in the scrap iron 43 

Suggestions for improvements in forging wrought iron gun- 
blocks 4.1 

Suggestions for improvements in casting and forging steel guu- 

blocks 51 

Smith's forge — Tools used in forging 52 

Building and management of the fires — Effects of overheating 
steel — The heat, how judged of — Tenacity and elasticity 

of steel increased by hammering 54 

"Upsetting — Welding iron to iron — Steel to iron — Steel to steel 

— Use of sand, borax, and sal-ammoniac in foi'ging 64 

Cutting bars of steel into short lengths 68 



CHAPTER V. 



ANNEALING. 

Steel — Cast iron — Copper 71 



CONTENTS. y 

CHAPTER VI. 

HARDENING AND TEMPERING OF STEEL. 

PAGE 

Introductory remarks — Hints to the mechanic on the manufac- 
ture of tools to be hardened 77 

Water not essential for hardening steel — Degrees of temperature 

required for hardening steel — Mode of applying the heat. . 91 

Art of tempering — Colors to be observed — Mode of applying the 

heat — Tempering steel with tallow and oil 95 

Rules to be observed previous to immersion — Temperature of 
water — Hardening in mercury, etc. — Mode of applying 
carbon to steel 106 

Advantage of hardening tools from the forge — Results of im- 
perfect cooling, flaws, breakages, etc 109 

Hardening and tempering circular cutters, dies, bushes, collars, 

ring gauges, etc 119 

. Various methods of hardening and tempering screw-taps, hobs, 

screw-dies, chasers, and screw-plates ' 140 

Various methods of hardening and tempering saws, rimers, 
small drills, gouge-bits, centre-bits, countersinks, gimblets, 
bradawls, etc 157 

Heating a steel plate in hot lead 171 

Hardening and tempering drifts, large drills, and chipping- 

chisels 178 

Method to give to steel a superior hardness without the use 
of mercury or saline liquids — Hardening and tempering 
spiral and other kinds of springs — Angled cutting-edges 
of tools and speed of lathe 184 



CHAPTER VII. 

EXPANSION AND CONTRACTION OP STEEL. 

Causes of expansion and contraction — Various methods of con- 
tracting holes in iron and steel 188 



10 CONTENTS. 

CHAPTER VHI. 

CASE-HARDENING WROUGHT IRON. 

PAGE 

By prussiate of potash — Animal charcoal 198 

CHAPTER IX. 

TOUGHENING OF STEEL IN OIL. 

Railway bars — Gun-blocks — Mode of heating gun-blocks — Tem- 
perature required — Fuel employed — Maimer in which the 
cooling is performed — Change which takes place in the 
steel by the operation — Cause of the change — Shot for 
piercing iron and steel clad structures — Suggestions for 
improvements in their manufacture 208 

Conclusion .' 220 



THE 



MANAGEMENT OF STEEL. 



CHAPTER I. 

MANUFACTUEE OF IROK 

It was not my original intention to have ex- 
plained the manufacture of iron, or the converting 
of iron into steel, or of casting steel into ingots ; 
more especially when so much has been already 
written upon these subjects by those better quali- 
fied than myself; but, in answer to inquiries, and 
knowing that my little work is not complete with- 
out it, especially as it is likely to come into the 
possession of many whom books of a superior class 
never reach, on account of the high price at which 
they are sold, I have resolved in this, the fourth 
edition, before explaining the processes of harden- 
ing and tempering steel, to introduce a slight 
sketch of the processes by which the material is 
prepared. 

Iron is a mineral, and in its native state is 
called iron ore ; it is probably the most abundant, 
useful, and valuable of all the metals ; in fact, its 



12 MANUFACTURE OF IKON. 

value is beyond all estimate. In nearly every 
country on the face of the globe, more or less of it 
has been discovered, and there is no doubt that it 
exists in all parts of the world ; and, from its ex- 
tensive and diversified utility, it is one of the most 
useful substances known. It is a metal of great 
antiquity, and it is quite probable that it has been 
known and used from the earliest ages. But the 
circumstances which first led to the discovery of 
the ores, and the processes for reducing them into 
the pure metal, I must leave to the antiquarian. 
It would also be vain or idle of me to attempt to 
describe the numberless uses to which iron is 
applied, when they are so well known. Iron is 
seldom found pure — that is, it is the most difficult 
metal to obtain in a state fit for use-: but it com- 
monly consists of an oxide of the metal — that is, it 
is in combination with oxygen. It is generally 
mixed with substances such as clay, flint, and other 
impurities ; and, when combined with these sub- 
stances in such quantity as to be worth separating, 
the substance is called ironstone, or iron ore, and it 
is from this that the pure metal is extracted. The 
origin of the ores is beyond our knowledge ; but, as 
an instance of the great Creator's wisdom in pro- 
viding for the comforts and welfare of mankind, 
those ingredients requisite for fusing and converting 
the ores into the pure metal, such as coal and lime- 
stone, are generally found in the same localities as 
the iron ores ; and in those countries where coal 
does not exist, wood is found in abundance. 

Iron appears to be the only metal whose solutions, 



MANUFACTURE OF IRON. 13 

or combinations with. oxvgen, are not of a noxious 
nature. Mineral waters containing iron strengthen 
and increase muscular action ; and in . chalybeates, 
form the best tonics medicine can boast. 

Iron is nearly eight times heavier than water ; 
its specific gravity is about 7.77. Its texture is 
fibrous ; it is of a bluish- white or peculiar gray 
color, and is susceptible of a high polish. It is 
hard and sonorous ; it also strikes fire with flint, 
and is highly elastic. For instance, if a bar is 
bent by pressure applied to it, and if this pressure 
does not exceed a certain quantity, the bar will re- 
sume its original form when the pressure is re- 
moved. It is also malleable, which is the property 
of extending or spreading under the hammer with- 
out cracking, but less so than gold, silver, or copper. 
It is also very ductile, a property similar to malle- 
ability, whereby it may be drawn out into wire 
without breaking. Its tenacity is very great, a 
property which enables it to sustain a very great 
pressure or force without crushing or breaking. In 
a cold state it is hard and stubborn, but at a red 
heat it is soft and pliable ; and, at a white or spark- 
ling heat, it may be welded either to itself or to 
steel. This is one of its greatest advantages. "When 
two pieces of iron are equally heated, nearly to a 
state of fusion, they appear to be covered with a 
strong glaze or varnish. When brought together, 
they may be united by repeated blows of the ham- 
mer, or under pressure, and the union will not be 
visible. Although fire makes it soft and flexible, 
so that it can be easily bent, cut, punched, 



14 MANUFACTURE OF IRON. 

hammered, welded, and fashioned to any desired 
shape, the difficulty of melting malleable iron is 
very great. It requires the greatest heat of a wind 
furnace ; but the nearer it approaches to fusion, the 
more malleable and ductile it becomes. 

Iron is employed for mechanical purposes in 
three states ; namely, that of cast iron, wrought 
iron, and steel. 

Cast iron is the metal in its first state, rendered 
fusible by its combination with those two sub- 
stances which .chemists distinguish by the name of 
carbon and oxygen. Cast iron is that which results 
from the fusion of the iron ore with charcoal, coal, 
or coke. Cast iron contains more carbon than steel ; 
and, though it is principally in the superabun- 
dance of its carbon that it differs from steel, still 
this is not the only cause of the difference between 
the properties of iron- in the two states ; for cast 
iron contains other impurities, which lessen the 
cohesion of its particles — impurities which steel is 
freed from. From its carbon, however, some cor- 
respondence in their characters is found to exist ; 
thus, some kinds of cast iron admit of being made 
hard or soft, nearly in the same manner as steel ; 
like steel, it assumes different degrees of hardness, 
according to the rapidity with which the pieces are 
allowed to cool. To harden cast iron, it requires 
to be heated to a higher degree of heat than that to 
which steel is subjected for the same purpose, and 
then suddenly cooled in cold water, which imparts 
to it whiteness of color, and brittleness and closeness 
of texture. Cast iron, when once hardened, will not 



MANUFACTURE OF IRON. 15 

admit, like steel, of that hardness being reduced 
by various gradations to any specific degree (called 
tempering) ; to soften materially, it must be sub- 
mitted for some time to a whitish heat, and then 
very gradually cooled. Cast iron may be termed 
an impure carbonized iron. 

"Wrought iron is the cast, or pig, iron, freed from 
carbon and oxygen, and may be termed a nearly 
pure decarbonized iron, and, which has previously 
been remarked, is hardly fusible. 

Steel is a combination of iron and carbon, in 
which the proportion of carbon is very small, vary- 
ing from one to two per cent., and occupies an in- 
termediate position between cast and wrought iron. 
Steel is less fusible than cast iron, but much more 
so than wrought iron. 

We will now, for a short time, leave the subject 
of the properties of the iron in these three states, 
and commence with the manufacture of iron. By 
so doing, I presume, the whole subject will be the 
better understood. 

From excavations called mines, by drainage, the 
employment of suitable machinery, and the industry 
of the miner, the ore is extracted in a very rough 
state from the bowels of the earth. It is this cir- 
cumstance which ranks it anions; minerals. The 
first process, after the ore has been taken from the 
vein, is to calcine or burn the stones (a process call- 
ed roasting), in order to expel the water, sulphur, 
arsenic, and other impurities with which the ores 
are combined, before being cast into the smel ting- 
furnace. The roasting is effected by kindling large 



16 MANUFACTURE OF IKON. 

fires in the open air, and spreading upon the fires 
layers of ironstone mixed with cinders, coke-dust, 
and small coal, or other combustibles, such as wood 
and charcoal. Sometimes the roasting is performed 
in a kiln. The fuel and ironstone are put in at the 
top, and the roasted metal is taken out at the bot- 
tom. The loss of weight by the process of roasting 
is considerable, and in proportion to the quality or 
purity of the ore ; the more impure, the greater the 
loss of weight. The process of roasting in the open 
air was at one time almost universally adopted ; 
but some years ago, a Scotch gentleman, Mr. Neilson, 
introduced the hot blast for smelting the ore — that 
is, drying and heating the air before it is forced into 
the furnace. This invention has proved very val- 
uable and economical. Since its introduction, the 
ore and fuel are frequently used in the raw state, 
and the process of roasting in the open air has been 
abandoned by many ironmasters. 

The next process is smelting ; the object of which 
is to produce the metal in a purer state, and to form 
of all the other substances (as far as it is practicable) 
oxides and slags. In the great iron-works, the ore, 
broken into small pieces and mixed with a portion 
of broken limestone, is thrown into the blast or 
smel ting-furnace with coke, coal, or charcoal, in due 
proportion. The fire is raised to an intense heat by 
the combustion of the fuel and by the forcing in of 
a current or blast of air, either in a cold or heated 
state. It may be well to state here, that earths 
when alone are scarcely alterable by the most in- 
tense heat. Lime, however, although very infusible 



MANUFACTURE OF IRON. 17 

alone, as a flux promotes the fusion of the other 
earths which the ores of iron contain. If slags and 
metal are rendered perfectly fluid they will separate, 
in consequence of their want of affinity and their 
difference in specific gravity. ISTow, pure lime is 
very seldom, if ever, found native, but always in 
combination with acids, particularly carbonic acid ; 
and in the intense heat of the smelting-furnace the 
limestone parts with its carbonic acid, and, com- 
bining with the earthy matters of the ironstone, 
forms with them a liquid slag. The metal, as it 
melts, is deoxidized, and, being the heaviest, sinks 
by its own gravity, through the fuel, to the bottom 
of the furnace ; more ore and fuel are supplied from 
the top, and the operation goes on until there is 
sufficient metal melted to constitute what is termed 
a charge, which rises almost to the aperture of the 
blast. The furnace is then tapped at the tap-hole, 
and the metal run off into moulds ; these lumps are 
called pigs of crude or cast iron, and, for purposes 
where hardness without flexibility is wanted, the 
iron in this state is extensively used. Of course, it 
will be necessary to remelt it to cast it into the 
required form. The iron in this state varies greatly 
in quality, as may easily be supposed, from the dif- 
ference of its chemical composition, some kinds being 
much purer than others. The quality of pig iron 
varies according to the purpose for which it is in- 
tended : it does not entirely depend upon the qual- 
ity of the ore, but partly upon the purity of the fuel 
and the treatment it undergoes. The quality of the 
iron will vary with the quanity of carbon it con- 



18 MANUFACTURE OF IKON. 

tains ; and those who are acquainted with and ac- 
customed to the smelting operations, can generally 
form an opinion as to the state and quality of the 
metal as it flows from the furnace, and also from its 
appearance when broken. 

The pig iron is assorted and classed by the iron- 
master as Nos. 1, 2, and 3, and differing in the 
amount of carbon combined. No. 1 is most highly 
carbonized, No. 2 less, and No. 3 contains the least. 
No. 1 runs so fluid as to be the most suitable for 
ornamental work ; it runs fine enough to fill the 
sharp angles and figures of the mould into which it 
is poured. Cast-iron cutlery is manufactured from 
No. 1, and the carbon subsequently extracted from 
the articles. This is done by heating them for a 
considerable time in a furnace, and surrounding them 
on all sides with some substance containing oxygen, 
such as the pure oxide of iron, or any earthy in- 
fusible powders free of sulphur. The articles obtain, 
by this process of annealing and purifying, a con- 
siderable degree of malleability, and it is not impos- 
sible to render them capable of being welded. For 
large works or castings, which require great strength, 
the iron which contains a smaller proportion of car- 
bon is preferable ; and that which has the least 
carbon, and is freest from other impurities, is prob- 
ably the most suitable for the manufacture of 
wrought iron. It may be observed, that the whiter 
the metal the harder it is also. 

Cast-metal articles are made from the iron just 
treated of. The pig iron is melted at the founderies, 
and runs in a state of fusion into moulds, either direct 



MANUFACTURE OF IKON. 19 

from the furnace by channels cut in the sand, or into 
ladles to be conveyed to the moulds, which are made 
of either iron, sand, or loam, according to the re- 
quired shape and size. The moulds (excepting those 
made of iron) are generally formed by means of a 
wood or iron pattern; which, sunk in the sand and 
then withdrawn, leaves a cavity of the desired form, 
into which the fluid metal is run. If the metal is 
large in quantity, it is agitated by the workman with 
an iron rod in order to consolidate the mass, and to 
get rid of any air or gas which may be confined in 
the metal ; after which it is allowed slowly to cool 
and crystallize. When cold the castings are taken 
out. It is a curious fact that if the rod used for 
agitating the metal be a slender one, it is quickly 
converted into steel, though of very indifferent qual- 
itp, which is a satisfactory proof that cast iron con- 
tains carbon, the steel-making principle. 

Having stated that wrought iron is nearly pure 
decarbonized iron, it remains to be shown in what 
way the decarbonization is effected. The first opera- 
tion for producing this change is called refining. The 
pig iron is remelted in a furnace, called a refining 
furnace, and kept in a state of fusion for some time, 
exposed to an intense heat, and a blast of air forced 
over its surface in order to remove some of the im- 
purities of the metal ; it is then run out of the fur- 
nace into a large flat mould, and acquires the name 
of plate metal. 

The succeeding process is called puddling ; the 
object in this process is to free the metal of its carbon 
and oxygen. The operation is performed in a rever- 



20 MANUFACTURE OF IRON. 

beratory or puddling furnace, where the cast metal 
is again reheated, and converted into wrought iron 
by keeping it in a state of fusion for a considerable 
time, and repeatedly stirring it in the furnace, by 
means of tools, through a small hole in the furnace, 
provided for that purpose ; the whole of the metal 
is thus exposed to the action of the oxygen passing 
over it from the fire, at the same time adding matters 
capable of yielding oxygen. When the whole mass 
has received an equally high temperature, the oxygen 
and carbon which it contains unite and fly off in the 
state of carbonic acid gas, and as this takes place 
the iron becomes more infusible ; it gets thick or 
stiff in the furnace, and grows increasingly so until 
it loses nearly all fluidity, and the workmen know 
by this appearance that it is time to submit it to the 
action of the hammer, or the pressure of a machine 
called a squeezer. The workman then divides, by 
means of his tools, the contents of the furnace into 
several parts, and forms them into separate balls. 
The balls being removed from the furnace, they are 
each subjected to a number of blows from a heavy 
steam hammer (called shingling), or to an intense 
pressure by a machine called a squeezer, by which 
the parts which still partake of the nature of crude 
or cast iron so much as to retain the fluid state are 
forced out, and the balls brought to an oblong shape, 
which is a shape more convenient for going through 
the rollers. The balls, after having undergone the 
first process of shingling by the hammer, or the 
squeezer, or any of the other machines invented for 
the purpose, are then called blooms. The bloom is 



MANUFACTURE OF IKON. 21 

then raised to the welding temperature in a reheat- 
ing furnace, and again submitted to the action of 
the hammer, or it is at once passed through large 
rollers having on their surfaces a series of grooves" 
varying in size, and when passed through these 
grooves in succession, the bloom is reduced and 
elongated to a flat bar, to the required width and 
thickness. The bars, after they have passed through 
these rollers, are cut into convenient lengths by the 
shears; they are then piled or fagoted together 
into convenient heaps. Several of these piles or 
heaps, each of which is composed of five or six bars, 
are placed at once in the furnace, and, when heated 
to the welding temperature, they are taken out 
separately, and are again passed through the rollers 
to reduce it to the form of a bar ; the grooves in 
these rollers differing according to the shape the 
bars are required, so that either round, square, flat, 
or various other shapes may be produced at the 
pleasure of the maker. Sometimes, in order to pro- 
duce a superior kind of iron, the cutting and welding 
and rolling is again repeated. "When charcoal is 
used as fuel in place of coal, or coke, for the manu- 
facture of iron, a superior kind of iron is obtained ; 
but, owing to the expense of charcoal, it is obvious 
that the iron thus made is more expensive. The 
bars having received their various shapes from the 
rollers, are then straightened and sheared to the re- 
quired sizes, weighed and ready for sale. By these 
processes the metal is thus converted from a fusible, 
hard, and brittle substance, into a tough and elastic 
bar ; in fact, it has been rendered malleable, ductile, 



22 MANUFACTURE OF IRON. 

more closely compacted, of a fibrous texture which 
is hardly fusible, and for purposes where lightness, 
strength, and durability is wanted, it is more exten- 
sively employed than cast iron. In this state it is 
known in commerce by the name of bar, or wrought 
iron ; and it may now be considered a nearly pure 
decarbonized iron, and is ready for the smith, and 
the converter, to be made up or fashioned into the 
thousand varieties of articles from a needle to Sir 
William Armstrong's six-hundred pounder. 

The loss of weight sustained by iron in the pro- 
cess of refining, puddling, hammering, and railing, is 
considerable, generally amounting to one-fourth, and 
sometimes to one-half. Forged or wrought iron, 
like cast iron, varies greatly in quality, according to 
purity and treatment in its manufacture. Thus, 
some kinds are only tough and malleable at certain 
temperatures, whilst other kinds are tough and mal- 
leable at all temperatures ; or, in other words, both 
when the iron is hot and when it is cold. There are 
four kinds of iron which require most to be treated 
of, the other kinds having qualities occupying inter- 
mediate positions between these varieties. Iron 
which is tough and malleable at all temperatures is 
the best and most useful, as it may be bent in any 
direction without breaking, both when it is hot and 
when it is cold. It may be known generally by the 
equable surface of the forged bar, which is free from 
cross fissures, or cracks in the edges, and by a clear, 
white, small grain, or rather fibrous texture. The 
best and toughest iron is that which has the best 
welding properties, and which bears the highest heat 



MANUFACTURE OF IKON. 23 

without injury, and which has most fibrous texture, 
and is of a clear grayish color. This fibrous ap- 
pearance is given by the resistance which its particles 
make to separation. The next best iron, which is 
also tough and malleable in all temperatures, and 
which bears a moderately high degree of heat with- 
out injury, and which has also good welding prop- 
erties, has a texture consisting of clear, whitish, 
small grains intermixed with fibres. Another kind 
is tough when it is heated, but brittle when cold, so 
brittle that it will sometimes break with a single 
blow of the hammer, or by a sudden jerk, which 
makes it unfit for axletrees, and other kinds of work 
where life and property are dependent upon it ; but 
for some kinds of work that are to be exposed to the 
weather it is very useful, as it will resist the action 
of the atmosphere better than the other kinds of 
forged iron, or, in other words, it is less liable to 
rust ; it may generally be distinguished by a texture 
consisting of large shining plates without any fibres. 
This kind of iron is generally called cold short iron. 
A fourth kind of iron (called hot short, or red short) 
is extremely brittle when hot, and malleable when 
cold. This kind of iron at a red heat will hardly 
bear to be turned over the beak-iron of the anvil 
into the shape of a ring, or collar, without breaking, 
neither will a small rod at the same heat stand-to have 
a hole pierced through it without splitting, and it is 
never used for superior kinds of work, for a defective 
forging is sure to be the result if it is used ; but 
owing to its being much cheaper than the superior 
kinds, and being very tough and ductile in its cold 



24 MANUFACTURE OF IKON. 

state, for many purposes it is a very useful iron. 
On the surface and edges of the bars of this kind of 
iron, cracks or fissures may be seen ; and its internal 
appearance is earthy, dull, and dark. The cause of 
the brittleness in these last two kinds of iron is sup- 
posed by some to be the presence of sulphur and 
phosphorus in the iron. The young inquiring mind 
may be, perhaps, inclined to inquire, How does 
sulphur and phosphorus get in the iron ? The aus we r 
is, these impurities are frequently combined more 
or less with the iron ores, and in the roasting process 
they may not have been properly got rid of ; or the 
iron may have absorbed these impurities from the 
fuel in the smelting furnace, and the subsequent 
processes of manufacture may not. have properly 
purified the iron ; but it is quite probable that there 
are other accidental causes which have the effect of 
rendering the iron brittle. There is no great diffi- 
culty in proving sulphur to be injurious to iron ; 
for, if a roll of sulphur (commonly called brimstone) 
be held in one hand, and a piece of white hot iron 
be pressed against it with the other hand, the 
two bodies combine and drop down together in a 
fluid state, and form a brittle compound, which is 
neither ductile nor malleable. It is an indisputable 
fact, and well known to any practical man working 
at the welding of iron, that sulphur is injurious to 
the iron ; for, if sulphur be present in the lire, the 
iron will not weld. 



CHAPTER II. 

MANUFACTURE OF STEEL. 

Steel is a compound of iron and carbon, some- 
times formed from wrought iron by beating tbe 
wrought iron in contact with carbon, and some- 
times formed from cast iron by depriving the cast 
iron of all impurities except a small portion of 
carbon. The proportions of iron and carbon vary 
in the different qualities of steel ; but in that used 
ordinarily, the carbon rarely exceeds two per cent. ; 
for some purposes it is as low as one per cent. 
Good ordinary tool steel contains about one and a 
half per cent, of carbon. Different kinds of iron 
produce steel of different characters, and differ- 
ent qualities of steel are used for different pur- 
poses. 

In this country the most common mode of man- 
ufacturing steel is by a process called cementation. 
Mr. Bessemer has, of late years, however, intro- 
duced an entirely new system of manufacturing 
steel. By his process steel can be manufactured of 
any degree of hardness direct from the cast iron, 
without the intermediate operation of rendering it 
malleable, or, in other words, without the interme- 
diate operation of puddling, etc. The principle of 
the process consists in directing a blast of cold air 
2 



26 MANUFACTURE OF STEEL. 

upon molten cast iron, the cold air ignites the car- 
bon contained in the cast iron, and causes an intense 
combustion, and the carbon is consumed ; and by 
this means the cast iron is decarbonized to the state 
of good tool steel, or to mild welding steel or to 
the state of malleable iron, according to the length 
of time the combustion is continued. As carbon 
has a strong affinity for oxygen, and cast iron con- 
taining more carbon than steel, and steel being a 
compound of iron and carbon, it will be seen read- 
ily that if all the impurities of the cast iron can be 
got rid of, and the process of combustion can be 
stopped when the metal is decarbonized to about 
one or one and a half per cent., good steel must be 
the product. Mr. Bessemer can manufacture steel, 
of any degree of hardness, by continuing the pro- 
cess of combustion until the whole of the carbon is 
consumed, and then adding the required quantity 
of carbon to form steel by a subsequent opera- 
tion. 

Mild cast steel, or welding cast steel, as it con- 
tains a smaller proportion of carbon than ordinary 
cast steel, is being more and more used, and is grad- 
ually superseding the use of cast and wrought iron ; 
and there is good reason to believe that steel of ex- 
cellent quality, for numerous purposes, will, at no 
distant period, be manufactured cheaper than 
wrought iron is now produced by the operation 
of puddling. 

The furnace in which iron is cemented and con- 
verted into steel, called a converting furnace, has 
the form of a large oven, constructed so as to form 



MANUFACTURE OF STEEL. 27 

in the interior of the oven two large and long cases, 
commonly called troughs or pots, and built of good 
fire-stone or fire-brick. Into each of these pots 
layers of the purest malleable iron bars, and layers 
of powdered charcoal, are packed horizontally one 
upon the other to a proper height and quantity 
according to the size of the pots, leaving room every 
way in the pots for the expansion of the metal when 
it becomes heated. The bars are cut to certain 
lengths, ten, twelve, or more feet, according to the 
lengths of the pots. A hole is left in the end of 
one of the pots, and three or four bars are placed 
in such a manner that they can be drawn out at 
any period of the process and examined. After the 
packing of the pots is completed the tops are cov- 
ered with a bed of sand or clay. This is to confine 
the carbon and exclude the atmospheric air. All 
the open spaces of the furnace are then closed, the 
fire is kindled, and the flame passes between, under, 
and around these pots on every side, and the whole 
is raised to a considerable intensity of heat. This 
heat is kept up for eight or ten days, according to 
the degree of hardness required. On the fifth or 
sixth day a test bar is drawn out of the converting 
pot for the purpose of judging whether the iron is 
at its proper heat, and to test the progress of the 
carbonization. At this period of the process the 
film of iron is generally distinguished in the centre 
of the bar, and the fire is generally kept up for a 
day or two longer in order that the iron may absorb 
more carbon. If, again, upon the trial of a bar, the 
cementation has extended to the centre, or, in other 



28 MANUFACTURE OF STEEL. 

words, if the bars of iron have absorbed the car- 
bonaceous principle to their innermost centre, the 
whole substance is converted into steel, and the 
work is complete. The fire is withdrawn or extin- 
guished by closing the vents, and the mass is left 
to cool for several days. The furnace may contain, 
according to its size, from ten to thirty tons of iron 
at each charge, and the whole process occupies 
fourteen or fifteen days. 

By this process, carbon, probably in the state 
of vapor, penetrates and combines with the iron, 
which is thus converted into steel. The properties 
of steel being influenced by the properties of the 
iron from which it is manufactured, those only who 
possess a knowledge of the properties of the iron 
used are enabled to prepare steel fitted for any re- 
quired purpose. 

The properties of iron are remarkably changed 
by cementation, and it acquires a small addition to 
its weight, in proportion to the carbon it has ab- 
sorbed from the charcoal. It is much more brittle 
and fusible than before, and loses much of its duc- 
tility and malleability, but gains in hardness, and 
elasticity, and sonorousness. The texture, which 
was originally fibrous, has by the process become 
granular ; and its surface acquires a blistered char- 
acter, and presents, when broken, a fracture much 
like inferior iron. 

The continuance of the process of cementation 
introduces more and more carbon ; and, if the ce- 
mentation be continued too long, or, if the heat be 
too intense, the steel becomes porous, more brittle 



MANUFACTURE OF STEEL. 29 

and more fusible, in which state it is more difficult 
to weld ; but, if it has not been over-cemented, it 
retains the property of welding, and may be welded 
either to itself or to iron. But the most impor- 
tant alteration in its properties is, that it can be 
hardened by heating it to a bright-red heat, and 
suddenly quenching it in cold water, which is a 
property it did not possess when in the state of 
pure malleable iron ; and it is to its carbon that 
it owes this most valuable property. By the 
application of heat, hardened steel may be softened 
down again to any requisite degree. The process 
of reducing the hardness of steel is called tem- 
pering. 

It may be well to state, that some kinds of mal- 
leable iron may also be hardened in a small degree 
by heating to a red heat and suddenly quenching 
in cold water ; but the effect is confined to the sur- 
face, except, as it very often happens, that the iron 
contains veins of steel. Pure malleable iron, how- 
ever, does not possess hardening properties ; it 
should be equally soft, whether suddenly or slowly 
cooled. Although pure malleable iron does not 
possess hardening properties, still, it is rendered 
more rigid by being suddenly cooled. This effect 
is owing to the compression of the particles into a 
denser state ; and, for some purposes where stiff- 
ness combined with a certain amount of flexibility 
is required, small lumps of pure malleable iron are 
the better for being immersed in water. 

The contractile forces of large lumps of malle- 
able iron when plunged into water will induce 



30 MANUFACTURE OF STEEL. 

strains, which have a tendency to rend open the 
interior of the mass. The water acting suddenly 
upon the surface causes the compression to be too 
sudden, consequently it would be disadvantageous 
to immerse a large mass of pure malleable iron in 
cold water. When a lump of pure malleable iron 
is required more rigid than when in its natural 
state, and less rigid than when immersed in cold 
water, it may be heated to a bright-red heat and. 
cooled in oil. The oil acting less suddenly than 
water upon the iron, it is obvious that an internal 
fracture is less likely to occur. 

Iron prepared by the process previously men- 
tioned is called blistered steel, from the blisters 
which appear on its surface, the blisters being 
caused by the long continuance of heat, and proba- 
bly the expansion of air within these blisters. 
When the bars of blistered steel are heated and 
drawn out into smaller bars by means of the ham- 
mer, it acquires the name of tilted steel. Spring 
steel is the blister steel, simply heated and rolled, 
but frequently the iron is specially cemented for 
spring steel; by the compression and elongation 
of its particles under the hammer, or between the 
rollers, the material is improved increasingly in a 
remarkable degree. 

Shear steel is produced by cutting the bars of 
blistered steel into convenient lengths, and piling 
and welding them together by means of a steam- 
hammer. Striking in rapid succession upon the 
steel, it closes the seams and removes the blisters. 
By this rapid hammering the steel is kept in better 



MANUFACTURE OF STEEL. 31 

temper, and fewer heats are required for the same 
work. The "bars, after being welded and drawn 
out, are again cut to convenient lengths, piled and 
welded, and again drawn out into bars. It is then 
called double shear steel ; hence the name single 
or double shear steel, according to the extent of the 
process of conversion. The bars are then ready for 
forging or rolling, according to the purposes for 
which it is designed. Shear steel breaks with a 
finer fracture, is tougher, and capable of receiving 
a finer and firmer edge and a higher polish than 
blistered or spring steel ; and, when well prepared, 
it is not much inferior to cast steel. Shear steel is 
very extensively used for those kinds of tools and 
pieces of work composed of steel and iron. 

Steel of cementation, however carefully made, 
is never quite equable in its texture, but the tex- 
ture of steel is rendered more uniform by fusion ; 
when it has undergone this operation it is cast 
steel. The best cast steel is produced by the inven- 
tion of Mr. Benjamin Huntsman, of Sheffield, long 
since deceased. It is nearly a hundred years since 
it was first invented, but the process still remains 
in principle unaltered. Cast steel is made from 
fragments of the blister steel of the steel- works. 
The process adopted is that of taking the blister 
steel, converted to a certain degree of hardness, 
and breaking it into pieces of convenient length, 
and weighing about a pound each ; small crucibles, 
made of the most refractory fire-clay, which are 
capable of holding about thirty pounds or more in 
weight, are then charged with these fragments, and 



32 MANUFACTURE OF STEEL. 

placed in furnaces similar to those used in brass- 
founderies. The furnaces are furnished with covers 
and chimney to increase the draught of air, and the 
crucibles are furnished with lids of clay to exclude 
the atmospheric air. The furnaces containing the 
crucibles are filled with coke ; and, for the perfect 
fusion of the steel, the most intense heat is kept up 
for two or three hours.' "When the steel is thoroughly 
melted, the melter, with a long pair of tongs, draws 
out of the fire the crucibles, and pours the contents 
in its then licprid state into ingot-moulds of the 
shape and size required. Although steel may be 
cast into ingots, it is too imperfectly fluid to be cast 
into very small articles. The crucibles, directly 
they are emptied, if they are sound, are returned 
into the furnace and again charged. The ingots 
of steel, once crude iron, but now changed by 
chemical action into cast steel, are taken to the 
forge or rolling-mill, and afterward prepared for 
the market by hammering or rolling into bars 
or plates, as may be required, in the same manner 
as other steel, but with less heat and with more 
precaution ; for the finest cast steel melts at a lower 
heat than any other steel, and is, therefore, more 
readily degraded in the fire, and is dispersed under 
the hammer or between the rollers, if heated to a 
white heat. Cast steel is the most uniform in qual- 
ity, the hardest and the most reliable steel for cut- 
ting tools, especially for those made entirely of steel ; 
and it is used for all the finest cutlery. Cast steel 
is dearer than the other kinds of steel, owing prin- 
cipally to the large quantity of fuel employed for 



MAISTUFACTUKE OF STEEL. 33 

its fusion. Its uniformity of texture enables it to 
take a line, firm edge, and receive the exquisite 
polish of which no other steel is in so high a degree 
susceptible ; and its unrivalled superiority is ac- 
knowledged in all parts of the globe. 



CIIAPTEK III. 

CHOOSING OF STEEL. 

It would be far easier for me to elioose good from 
Lad tool steel than to describe how to choose it. 
However, it may be well to state that, in choosing 
steel for cutting-tools, where tenacity as well as 
hardness is required, some technical knowledge is 
requisite ; although the differences of steel consist 
in its composition, it is not always necessary to sub- 
ject it to chemical analysis in order to know its 
nature or character. The hardness and tenacity of 
steel, and the other properties of forging and weld- 
ing, are very useful in distinguishing its qualities ; 
but it is also necessary to ascertain these properties 
with precision. Marks or signs, by wdiich to know 
by sight, by sound, or by strength, good tool steel, 
are doubtless fallacious. Sight may afford some- 
times an idea of the quality of steel, but it cannot 
be depended upon ; even with great experience the 
result is always uncertain. The usual method of 
choosing steel for tools, which require a fine, firm 
edge, is to break a bar, and to observe its fracture 
and select that which has a moderately fine grain ; 
but this method is not always certain, as a variation 
in the fracture will be caused by the hardness or 
softness of the steel, or, in other words, by the dil- 



CHOOSING OF STEEL. 35 

ference of it's temper, and the greater or less heat 
at which it has been hammered or rolled, and some 
steel • breaks of a very close grain, though of very 
indifferent quality. Several methods may be prac- 
tised to ascertain the goodness of the steel, but if 
there is an opportunity of forging some of the steel, 
it is advisable to do so ; for, in my opinion, there is 
no better means of ascertaining its true character. 
In the first place it will be requisite to ascertain the 
highest degree of heat the steel will bear without 
injury, and then to keep always a little below this 
heat. Steel will not bear the same degree of heat, 
without injury, as iron; and steel which will not 
bear a high heat in forging will not bear a high 
heat in hardening. Blistered steel will resist a far 
higher degree of heat than highly carbonized cast 
steel, and good shear steel will endure a white flame 
heat without much injury; also a welding heat, if 
subsequently hammered. Although iron will bear 
a higher degree of heat than steel, yet steel will 
bear a far greater amount of hardship under the 
hammer than iron — that is, if the steel is cautiously 
heated. Good cast steel, which is suitable for the 
best kinds of cutting-tools which have to endure a 
great amount of hard work, will not bear a white 
heat without falling to pieces ; it will hardly sustain 
a bright-red heat without crumbling under the 
hammer, but at a middling or cherry -red heat it 
will bear drawing under the hammer to a point as 
fine as a needle. Inferior steel, whether at a high 
or low heat, will not take such a fine point without 
splitting ; and steel which will not take a fine point 



36 CHOOSING OF STEEL. 

will not receive a fine, firm edge, however skilfully 
the hardening and tempering may be performed. 

There are some kinds of steel which are very 
tenacious, and which will take a moderately fine 
sound point, but, found deficient in their hardening 
properties, must be rejected for the best kinds of 
tools. Drawing a piece of steel to a point for test- 
ing it is a simple process ; but, simple as it is, without 
some degree of attention it may produce false results 
and mislead the unwary. For instance, suppose we 
were to take a piece of steel cut from a bar, and 
commence to draw the extreme end of it to a point, 
if the extreme end of this piece of steel should happen 
to be even in a small degree concave, previous to 
hammering it, we cannot succeed in getting a fine 
sound point, although the steel should be the best 
Sheffield can furnish ; for, in hammering it, the sur- 
face steel will overrun the centre, and cause the 
extreme end to be concave in a greater degree, and 
so long as this concavity exists in the end the steel 
cannot take a fine sound point. To avoid this, pre- 
vious to commencing to draw the steel to a point, 
the extreme end of the piece of steel under trial may 
be either ground or filed to a roundecLpoint similar 
to a centre punch but not quite so sharp ; and, if the 
steel is tenacious, we will then succeed in drawing it 
to a fine sound point. Another method is to take a 
piece of steel just as it is cut or broken from a bar, 
without filing or grinding the end ; heat one end of 
it to a cherry-red heat, and place it upon the project- 
ing arm of the anvil, called the beak-iron ; the extreme 
end of the steel must be allowed to project over the 



CHOOSING OF STEEL. 37 

beak-iron so as not to make use of it, and then draw 
the steel to a gradually tapered square point ; the 
small piece which was allowed to project over the 
beak-iron must now be taken off by filing the steel 
through at the smallest part, after which it must be 
reheated and drawn to a finer point — that is, of 
course, if the steel will take a finer point without 
splitting. A welding heat will of course be required 
to test the welding properties of steel, but a welding 
heat should not be used when drawing the steel to a 
point to test its tenacity under the hammer. The 
extreme end of a bar of steel, in the state it leaves 
the tilt or the rollers, should not be taken for testing 
the quality of the steel; it should be rejected on 
account that it is looser and more porous than the 
other parts of the bar. For the sake of having a 
clearer idea of our subject, let us suppose the piece 
of steel to have received a fine sound point, and to 
be possessed of tenacity ; the next operation will be 
to test its hardening properties, and to ascertain the 
degree of its tenacity. Tenacity is an opposite 
quality to brittleness ; therefore, if the hardness is 
not accompanied with a certain degree of tenacity 
the steel will be of very little service for the best 
kinds of cutting-tools or for surgical instruments; 
therefore it becomes an object of importance to at- 
tend to this trial most carefully. The fine point of 
this piece of steel under trial may now be cut off, 
and the steel drawn out again under a low heat to 
a gradually tapered square point, but not so fine as 
before ; it must then be plunged suddenly at this 
heat into pure cold water ; the hardened point may 



38 CHOOSING OF STEEL. 

then be tried with a smooth file, but I may state 
that this mode of trial with a file is defective, as 
files differ in hardness and only serve to tell in an 
imperfect manner the hardness of the steel ; but if 
the point be broken off just enough to show the 
fracture, and it will easily scratch glass, it is a 
positive proof that the steel is hard and possessed 
of good hardening properties. The power used in 
breaking affords some knowledge of the tenacity of 
the steel. The broken point may be tried, and the 
degree of the tenacity of the steel ascertained, by 
placing it upon a piece of hard cast iron and 
crushing it under the face of a small hardened 
hammer; if the steel is good it will resist the 
crushing, and will cut the hammer's face, and bury 
itself in the cast iron. Inferior steel, having little 
or no tenacity, by this test will be ground to powder 
or crushed flat, nearly as easily as a piece of hard 
iron, and will not enter the cast iron. The degree 
of resistance of this grain of steel to the crushing 
power is a good rule by which to judge of it, for 
many kinds of steel feel hard to the file and yet show 
no tenacity. If the steel under trial will take a fine 
sound point, and after plunging it when red hot into 
pure cold water require a moderate force to break 
it, prove hard and will easily scratch glass and resist 
the crushing power, whatever its fracture may be it 
is good. The excellence of steel will always be in 
proportion to the degree of its tenacity in its hard 
state. 

Another mode of trial, more simple and more 
economical, and less delicate than the former, and 



CHOOSING OF STEEL. 39 

on the results of which full reliance may be placed, 
is carefully to forge a flat and a diamond-pointed 
chipping-chisel, which must be carefully hardened 
and afterward tempered to a violet color, after 
which to be ground upon the grinding-stone, and 
then tested upon a piece of hard cast iron. If the 
chisels resist the blows of the hammer without break- 
ing, and "keep a sharp, firm edge, full reliance may 
be placed on the quality of the steel ; for in my 
opinion there is nothing which will indicate the 
quality of the steel better than a diamond-pointed 
chisel tested upon a piece of hard cast iron ; for it 
supplies us precisely with the information we are 
seeking, namely, whether hardness and tenacity are 
combined in the steel. If the chisels prove good 
there is no waste of steel, for the result of the test is 
two good and useful tools. If the steel does not 
prove satisfactory, the chisels need not be wasted, 
for they may be easily altered into either round, 
square, or flat punches for piercing hot iron ; for the 
steel would be very bad indeed if it would not do 
for this purpose — so bad, that it could be readily 
detected by the eye in the first instance when the 
bar was broken. In general, in its soft state, a curved- 
line fracture and uniform gray texture denotes 
good steel ; and the appearance of threads, cracks, 
or sparkling particles is a proof of the contrary. 

Good tool steel in its hard state on fracture pre- 
sents a dull silvery appearance, is more close in its 
texture than annealed steel, and is of a uniformly 
white color, with the entire absence of sparkling 
particles. If aquafortis be applied to the surface 



40 CHOOSING OF STEEL. 

of steel previously brightened, it immediately pro- 
duces a black spot ; but if applied to iron the metal 
remains clean, so that it will be quite easy to select 
such pieces of iron or steel which possess the great- 
est degree of uniformity, as the smallest vein, either 
of iron or steel, upon the surface, will be distinguished 
by its peculiar sign. 



CHAPTEK IV. 

FORGING AND WELDING IRON AND. STEEL. 

The forge, furnished with furnaces, steam-ham- 
mers, cranes, anvils, swage-blocks, and various other 
kinds of tools, is the workshop in which iron and 
steel are welded and fashioned with the hammer. 
"Welding is that operation by which pieces of iron 
or steel, or steel and iron, are equally heated nearly 
to a state of fusion and appear to be covered with 
a strong glaze or varnish, are brought together and 
united by repeated blows of the hammer or under 
pressure, and the union not to be perceived. 

The heat the iron receives in forging is judged 
by the eye, and is not commonly distinguished into 
more than these five degrees, namely, the dark-red 
heat, the blood or low cherry-red heat, the bright 
cherry-red heat, the white-flame heat, and the spark- 
ling or welding heat. 

The dark-red heat is not visible in daylight, but 
shines in the dark with a brown color, and is used 
only when stiffness and elasticity are required. 

The blood or low cherry-red heat is used to give a 
fine polish or skin to the iron. 

The bright cherry-red heat gives the thin scale or 
oxide on the iron a black a]:>pearance ; and forgings 



42 FORGING AND WELDING IRON AND STEEL. 

of any description ought to be smoothed and finished, 
at this heat. 

The white-flame heat is that which gives the 
scales and the iron the same color, and is used for 
forging, or changing the form, of iron when weld- 
ing is not required. 

The sparkling or welding heat is that which 
gives the iron the appearance of being covered with 
a glaze of varnish, and is used for uniting two or 
more pieces of iron together, or a multiplicity of 
pieces into a solid mass. 

The heat required for welding iron varies in some 
degree with the purity of the iron. Pure fibrous 
iron will bear almost any degree of heat without 
much injury, if not too long exposed to the heat ; 
while impure iron bears but a moderate degree of 
heat without being melted or burnt. 

Although iron requires to be heated nearly to a 
state of fusion before it can be welded (at least when 
heat alone is applied), still care must be taken to 
prevent the iron from running, or it will make it so 
brittle as to prevent its forging, and sometimes so 
hard -as to resist the cutting-tool, or the file. This 
accident will sometimes occur with the most skil- 
ful workman ; and, when it does occur, the whole 
of the iron which is injured by the extreme heat 
should be cut off and rejected. If it cannot con- 
veniently be cut off, the whole of the forging ought 
to be rejected, more especially if life or property is 
depending upon it. 

The ordinary fuel used for the forging of iron in 
this country is coal ; and, from its abundance and 



FOKGING AND WELDING LEON AND STEEL. 43 

cheapness, it is more frequently used in forging 
steel than either coke or charcoal. Charcoal, on ac- 
count of its purity compared with other kinds of 
fuel, is undoubtedly the best fuel that can be used 
for the heating of steel ; but, owing to the scarcity 
of wood in this country, which makes it so expensive, 
it is seldom used. Coke, cinders, and turf are the 
next best kinds of fuel for heating steel. Dry coal- 
dust is injurious to steel. 

The heaviest works or forgings are generally 
heated in air furnaces ; and the heavy iron forgings 
are usually made up of scrap iron. The scrap iron 
is cut up into small pieces by the shears ; it is then 
piled or fagoted into convenient-sized masses of 
one or two hundred weight, and placed in the fur- 
nace. The fire is urged, and the mass is raised to 
the welding heat ; it is then withdrawn, and placed 
under the hammer, and united into a bloom or slab. 

Blooms and slabs are sometimes made of the 
shavings that are cut from the iron at the turning 
or boring lathes. From one to two hundred weight 
of the shavings are thrown into ' the furnace, and 
spread evenly over the bottom ; the fire is urged, 
and the workman observes through a small hole in 
the furnace-door provided for the purpose, and for 
the introduction of his tools, the progress of the 
heat. As soon as the iron arrives at the welding 
temperature, the workman collects it, and makes 
it up by means of his tools (a rod of iron with an 
eye at one end, and a hook at the other), and 
while it is yet in the furnace, into a spherical 
form ; he then rolls it about in the furnace, so as to 



44 FORGING AND WELDING IRON AND STEEL. 

insure an equable temperature to the mass, after 
which the furnace-door is lifted, and the hall remov- 
ed from the furnace by means of a hand-truck ; the 
workman then grips it with a pair of tongs, and 
shingles it under a heavy hammer into a square or 
oblong bloom ; after which the bloom is reheated to 
the welding temperature, and subjected to a second 
hammering, in order to get rid of all the dirt, or 
scoria, which may have got closed up with the iron. 
In order to make it more compact, and more thor- 
oughly to condense the particles, it is then hammer- 
ed into the form of a flat slab. Several of these 
slabs heated, and welded together, form the masses 
of which large forgings are generally built up. 

"When a mass is too large to be handled conve- 
niently by the forgeman with the tongs, a large iron 
rod is welded to it, to serve as a porter or guide-rod, 
and the welding of the rod to the mass is performed 
in a variety of ways. The end of the rod is sometimes 
inserted into the mass within the furnace ; and, 
when the whole is at the welding temperature, the 
other end of the rod is struck with the sledge-hammer, 
which welds it sufficiently to lift the mass from the 
furnace to the hammer. Sometimes the end of the 
rod is heated in a separate part of the furnace, and 
made to arrive at the welding temperature at the 
same time as the mass ; and, when the mass is with- 
drawn from the furnace, the rod is withdrawn also, 
and generally welded on by the first blow of the 
hammer. Sometimes a part of the porter-bar is 
made to form the core of the forgings, and the slabs 
or masses of iron which form the forgings are welded 



FOKGING AND WELDING IRON AND STEEL. 45 

and built upon the bar. When a mass of iron or 
forging is too large to be handled by the forgeuian 
with the porter or guide-rod, it is supported by a 
crane, which serves to swing it from the fire to the 
hammer ; likewise it serves for the different changes 
of elevation which the work at times requires ; it 
serves also for moving the work to and fro upon the 
anvil. A cross lever is temporarily fixed to the 
porter, the use of which is to enable the workmen to 
turn the work over so as to expose all the parts to 
the action of the hammer, when it is manipulated 
with the greatest ease ; and the mere sight of the 
welding and manipulation of large masses of iron, 
when conducted by a skilful workman, is always 
interesting, even when of every-day occurrence. 

The mingling of the fibres in the scrap iron is 
generally considered highly favorable to the strength 
of the forging, which probably it is when the scrap 
iron is of good quality ; but scrap iron of an inferior 
quality, or a mixture of all qualities (however skil- 
fully the operation of forging and welding may be 
performed), can never produce a forging so good as 
new bar iron of good quality, cut up into lengths, 
piled, and welded. 

The mingling of the good iron with the bad iron 
probably does have the effect of improving the bad 
iron ; but the bad iron cannot have the effect of im- 
proving the good iron. But it may be said that the 
hammering has the effect of improving the bad iron, 
and without a doubt it does do so to a certain degree ; 
and, if hammering improves bad iron, it must cer- 
tainly improve good iron to a certain degree also, 



46 FOKGING AND WELDING IKON AND STEEL. 

thus showing that new bar iron of good quality must 
certainly produce a better forging than scrap iron of 
bad quality, or scrap iron of all qualities ; for the 
forging must certainly be more uniform in metal, and 
more uniform in temper, consequently it must be 
more uniform in elasticity and tenacity. The quality 
of iron is much improved by violent compression, 
such as by forging and rolling. It gives much greater 
strength to the iron, by its being elongated and solid- 
ified, especially when it is not long exposed to vio- 
lent heat; but when it is long exposed to violent 
heat, its particles undergo an injurious change of 
position, and the heat at length destroys its metallic 
properties ; but, though iron is rendered malleable 
by hammering, still this operation may be continued 
so long as to deprive it of its malleability, also its 
fibrous character ; and the more readily with the 
absence of a sufficient degree of heat. 

When a large solid forging is required perfectly 
sound throughout the mass, and which is made up 
either with scrap or new bar iron, there is no better 
method than to forge it square ; that is, with four 
flat sides. This plan is seldom adopted with a for- 
ging which is required round, on account of a greater 
amount of time being required to turn it in the turn- 
ing-lathe. Though this method is seldom adopted, 
it does not make it any the less effective in produ- 
cing the soundest forging ; as it must be evident to 
those who have ever thought at all upon the subject, 
that large forgings, which are hammered or forged 
round upon flat surfaces, or between the half circle 
swage-tools, or even between the V swage-tools, can 



FORGING- AND WELDING IKON AND STEEL. 47 

never be so dense and solid as forgings which are 
forged square (with four " flat sides). A forging 
forged with six sides will always be denser and more 
solid than a forging which is forged round between 
flat surfaces ; but it will be less dense, and less solid, 
than a forging forged with four flat sides, for these 
reasons, that the larger the squares, the more iron 
there is under compression at the same time, conse- 
quently -the denser and more solid the forging be- 
comes. Forgings made in dies are prevented from 
becoming hollow in the centre ; but, with very 
large forgings, this method is quite impracticable. 

When a forging is being made round between 
flat surfaces, there is such a small quantity of the 
whole mass under compression at one time, that 
every blow of the hammer tends to make the forging 
hollow or porous in the centre by forcing out the 
sides of the forging at every successive blow ; the 
greater the force of the blows, the greater the effect 
in causing the forging to become hollow (commonly 
called spongy) at the centre ; the less the force of 
the blows, the greater the effect in causing the for- 
ging to become hollow at the part between the sur- 
face and the centre, as every blow of the hammer 
has the effect of drawing and enlarging the outer 
case of the metal more than the inner part ; conse- 
quently it must have a tendency to separate the outer 
part from the inner part. 

It is more than probable that a very strong cy- 
lindrical iron forging (suitable for a gun, or for one 
of the parts of a built-up gun) may be made by 
taking six Y-shape rolled slabs, then to place them 



48 FORGING- AND WELDING IRON AND STEEL. 

round a suitable core of iron, then to heat the whole 
to the proper welding temperature, and then ham- 
mering upon the six sides, and welding the whole 
into a solid mass. The mass may subsequently be 
rounded between V swage-blocks ; this will form a 
good foundation upon which to build a greater 
amount of iron. 

It is quite probable (when rolling these slabs) 
that a projection could be left in one, two, or more 
places, upon one side of them, and in their opposite 
sides a kind of groove or cutting to correspond (as 
near as it would be practicable to make them) with 
these projections, so that with a little rough fitting 
these slabs could be dovetailed together, and made 
to hold themselves together whilst being heated in 
the furnace. Plain slabs could be held together by 
shrinking two or more rings upon them, or they 
could be held together by dovetailing short pieces 
of bar iron into them. After the slabs are welded 
into a solid mass and rounded between the swage- 
blocks, a series of thick rings (made of rolled bar 
iron) must then be placed and welded upon the 
mass. These rings must not be welded up pre- 
vious to welding them upon the mass, neither must 
they be formed by coiling a long bar upon the 
mass ; the two ends of each ring will require 
to be scarfed in order that they may slightly 
overlap each other when placed upon the mass, 
and not to form what is called a butt joint. The 
rings being ready, the forged mass must now be 
boated to a white-flame heat; it must then be drawn 
out of the furnace, and the thick scale or oxide 



EOKGING AND WELDING IRON" AND STEEL. 49 

scraped off; after which, several of these thick 
iron rings (or as many as may be convenient) 
must be placed side by side upon it ; the rings 
should be placed in such positions that their scarfed 
joints may not run in a straight line with each 
other ; they may then be closed upon the forged 
mass between Y swage-blocks. The whole must 
now be placed in a suitable furnace, and uniformly 
heated to the welding temperature ; after which, it 
must be brought to the hammer, and the whole weld- 
ed between large Y swage-blocks ; several more of 
the rings must then be placed upon the mass, and 
side by side with the first rings, and then heated and 
welded in a similar manner as the others, and so on 
until the desired length is obtained. If it is found 
more convenient to place and weld the whole of 
the rings at once upon the mass, it is advisable 
to do so ; for the fewer the heats the better the 
forging. 

By the above method, very few heats will be re- 
quired ; and we will have the fibre of iron running 
in the direction of the length of the forging, as well 
as in the direction of the circumference. The di- 
rection of the fibre is the strongest way of iron ; 
and, let whatever method be adopted, we can only 
get the strength of the iron. To have the fibre of 
the iron running in the direction of the length of 
a rifled gun is probably of the greatest impor- 
tance. 

Steel, like iron, is improved by hammering and 
rolling ; consequently, when a large cast-steel block 
is required of great tenacity for a particular pur- 



50 FORGING AND WELDING IRON AND STEEL. 

pose, the metal is not run into a mould of the shape 
and size of the required finished dimensions, but it 
is cast into a short thick ingot and then hammered 
and drawn to the required finished dimensions, or it 
is rolled to the required finished dimensions between 
the rollers. Although the steel is improved by 
being elongated and solidified, still it is question- 
able whether this is the best way of producing the 
soundest steel block suitable for a large gun. If 
every particle of the metal could be made to be 
come cool at the same moment, there would then 
be no question about this being the best method ; 
but it must be borue in mind that a large mass of 
fluid steel cools very unequally : it cools in layers, 
and closes up like a series of hoops, and is subject 
to very great strains. It is obvious, then, that after 
the block is drawn out to the required finished di- 
mensions, it still consists of the same number of 
layers ; the layers of course are reduced in thickness, 
which is unfavorable to the strength of the block. 
These layers frequently have so feeble a cohesion 
as to allow of their separation by a very light 
blow. 

For the reasons here given, we may conclude 
that, the thicker and the less in number these layers, 
the stronger the block must be. 

It is quite probable, then, that the soundest for- 
ging may be produced by casting the block square 
at the breech end, and in order to save steel, to cast 
the other part of the block with six sides ; the block 
may be cast longer and smaller in diameter than the 
required finished dimensions ; then to upset it, so as 



FORGING- AND WELDING IRON AND STEEL. 51 

to make it shorter and larger in diameter than the 
required finished dimensions ; it may then be elon- 
gated and solidified by drawing it out again by the 
hammer to the required finished dimensions. The 
breech end should be hammered and left square, 
and the other parts of the block (after hammering 
upon its six sides) rounded between half circles or 
V swage-tools (the V swage-tools most preferred). 

Casting a steel block of the proposed shape, and 
giving it the proposed subsequent treatment, would 
cause more waste of steel, and raise the cost of the 
block ; but it is quite probable that the superior 
soundness of it would more than compensate for the 
waste of metal, especially when the block is intended 
for the largest-size gun. If it is intended to toughen 
this block of steel in oil, it may then be asked, 
perhaps, whether it is necessary to leave the breech 
end square until after it has passed through the 
process of toughening, or whether it will be better 
to turn it round. The answer is, if the block is 
bored out to form a tube with a solid end, previous 
to toughening of it, it will then be better to turn 
it round; but it is more than probable, if the 
part which is left solid is left square also, that 
it will favor the contraction in cooling ; but it is 
not absolutely necessary to leave even this part 
square, but the extreme end may be turned and left 
concave in a slight degree. 

If it was intended to heat and immerse the block 
in oil previous to boring of it, it would be better to 
leave it square (in the state it left the forge) until it 
had passed through the process ; but to attempt to 



52 FORGING AND WELDING IRON AND STEEL. 

toughen it in its solid state would be a step in the 
wronfr direction, as it would be sure to break. 

A common smith's forge is the hearth or fire- 
place upon which ignited fuel is placed, and it very 
frequently consists of masonry or brick-work. It 
is furnished with a water-tank and coal-trough, also 
with a pair of bellows for supplying the air. The 
bellows are worked by a hand lever ; the small end 
of the pipe of the bellows passes through the back 
of the forge, where it is fixed in a strong iron plate, 
called a tue iron or patent back, in order to preserve 
the bellows from injury and the back of the forge 
from requiring frequent repair. The best position 
for the bellows is on a level with the fire-place, al- 
though they are often placed higher, and the blast 
of air passes through a bent tube, in order to gain 
room. 

Above the fire-place is a hood, which is some- 
times formed of bricks, but it is more generally made 
of plate iron; this serves to collect the dust and the 
smoke from the fire, and leads it to the chimney, 
and thus prevents it from flying about the shop. 
The more modern forge is made entirely of iron ; 
and the blast of air is supplied by a revolving fan, 
worked by an engine. The blast is communicated 
by a main pipe all round the smithy, and every fire 
has a branch pipe with a valve and handle fitted to 
it for regulating the blast. The tue iron at the back 
of this kind of forge is sometimes made hollow, so 
tli at a stream of water may circulate through it from 
a small tank placed behind the forge. The water 
keeps the tue iron from burning, or getting very hot, 



FORGING AND WELDING IKON AND STEEL. 53 

consequently it will last much longer than the solid 
tue iron ; but, if the tank is not kept well supplied 
with water, this kind of tue iron will burn away 
much sooner than the others. Clean water should 
always be put into the tank, and the tank should be 
supplied with a cover to keep out dust and dirt'. 

A light crane is sometimes erected near the forge 
for managing the heaviest kinds of work done by 
hand forging. The forge is also furnished with a 
poker, shovel, and rake. In the smithy there are 
anvils, hammers, swage-blocks, natters, tongs, chisels, 
gouges, top and bottom fullers, top and bottom 
swage-tools, drifts, mandrels, flat, square, and round 
punches, and a multiplicity of other tools of various 
shapes and sizes ; and it is an object of much im- 
portance to have the hammers and other tools per- 
fectly well secured to the handles, to prevent serious 
accidents. 

Forges are sometimes constructed so as to be 
portable, when the bellows are most conveniently 
placed under the hearth, and worked by a treadle 
or hand lever. Sometimes the blast is supplied by 
a small revolving fan, attached to the forge; the 
fan is driven by a fly-wheel, turned by hand. Port- 
able forges are generally made of iron, and those 
with the revolving fan are generally erected upon 
wheels, and are generally used by the amateur me- 
chanic, by boiler-makers for heating the rivets, and 
repairing their tools. Also on ships, and for various 
jobs on bridges, railways, etc. 

For forging iron and steel, for hardening and 
annealing steel, the fire at the comuron forge is some- 



54 FOEGLNG AND WELDING IKON AND STEEL. 

times made open, and sometimes hollow. The fires 
are commonly of three kinds. The flat open fire, 
the stock hollow fire, and the stock open fire ; the 
size of which must be regulated by the requirements 
of the work. 

ffiie flat open fire, when allowed to burn itself 
bright or clear, is ready for the insertion of the 
work. This kind is generally used for forging and 
welding small kinds of work, such as the welding 
of small iron rods together, and the forging of small 
bolts and nuts, rivets, and small tools ; in short, it 
is used for almost all single-handed^work, and foi 
some which is called double-handed work (that is, 
where the smith has an assistant). 

The stock hollow fire for fore-ino; iron is made 
by inserting the tapered end of a bar of round iron 
into the tue iron, after which a quantity of small 
wet coal is thrown upon the hearth and beat- 
en hard round the bar with the sledge-hammer; 
more coal is then added, and the hammering again 
repeated ; and so on, till the coal above the bar is 
several inches in thickness, and^ibout one foot more 
or less in width and length. After the hammering 
is completed, it is beaten close together with the 
slice or shovel to form a kind of embankment. This 
is called the stock. The bar is then withdrawn, the 
slice or shovel at the same time being held against 
the front of the stock to prevent the bar from break- 
ing the front down. A second stock is then made 
opposite the first, but without the hole through the 
centre of it, as in the first stock. A fire is then 
made between the two stocks, and the work laid in 



FORGING AND WELDING IRON AND STEEL. 55 

the fire ; the work is then covered over with some 
thin pieces of wood and some small pieces of coke, 
after which small damp coal is thrown on in a layer 
of several inches thick, and beaten clown with the 
slice to form the roof. A steady blast is kept up 
all the time, and as the wood burns away the flame 
peeps through and forms the mouth of the fire ; but 
the work is not moved till all the wood is burnt out, 
and the coal well caked together into a hard mass. 
More blast is then driven in, and the roof of the fire 
reflects an immense heat upon the work below it. 
After which the work can be moved about in the 
fire or withdrawn without risk of breaking clown the 
fire. A lump of hard coke is generally placed 
against the mouth of the fire to confine the heat ; 
and as the fuel in the inside burns away it is re- 
placed by pushing in some small coal, or soft coke. 
Sometimes a small quantity of hard coke broken 
into small pieces is pushed in to give body or sub- 
stance to the fire. This kind of fire is sufficiently 
powerful for a moderate share of those works which 
require the use of a light crane and the steam-ham- 
mer, and which cannot conveniently be heated in a 
furnace ; it is used for welding shafts together, also 
for welding collars upon shafts, and various other 
kinds of work requiring the assistance of one, two, 
or more men ; it is also used for giving a uniform 
temperature to large lumps of steel, but in heating 
this material it must be borne in mind that the blast 
must "be sparingly used. 

The stock open fire is made the same way a^ 
the stock hollow fire, with the exception of the 



56 FORGING- AND WELDING IKON AND STEEL. 



covering- in or roof. This is the most convenient 
fire for heating the steel when forging tools ; it is 
also the most convenient for heating those kinds 
of tools requiring only to be partially heated and 
partially hardened, the remaining part requiring to 
be kept soft, such as cutting-tools for the turning- 
lathe, cold chisels, drills, etc.; but for those kinds of 
tools which require to be heated all over or through- 
out their body, such as screw-taps, dies, circular 
cutters, etc., the hollow fire is the most convenient. 

The hollow fire for heating the steel for harden- 
ing is built in a similar manner as the hollow fire 
for heating steel for forging, with the exception that 
a larger quantity of wood is required for centring 
the arch. 

In forging at the common forge, the fire of course 
must be regulated by the size of the work ; and, in 
heating the work, if the flame break out, the coals 
must be beat together with the slice to prevent the 
heat from escaping. The fire should be free from 
sulphur, brass, copper, lead, tin, paint, or any other 
thing which would keep the iron from welding. To 
save fuel damp the coal, and throw water on the fire 
if it extends beyond its proper limits. To ascertain 
the state of the work it must be drawn partly out of 
the fire — that is, when the open fire is used — and 
thrust quickly in again if not hot enough. To make 
the iron come sooner to a welding heat, stir the fire 
with the poker and throw out the clinkers, as they 
will prevent the coals from burning. Care should be 
taken, cither with iron or steel, not to use a higher 
degree of heat than is absolutely necessary to effect 



FO-RGESTG- AND WELDETO IKON AND STEEL. 57 

the desired purpose, with steel especially to use as few 
heats as possible. The too frequent and excessive 
heating of steel abstracts the carbon, and gradually 
reduces it to the state of forged iron again. This, 
perhaps, calls for a little explanation. When steel 
is at a low heat the carbon has a very slight affinity 
for oxygen ; hence the steel suffers little change — 
the change which does take place is so slow that it 
is not perceptible till after many repeated heatings ; 
bat when steel is heated to a high degree in the 
open fire in the presence of oxygen, the surface be- 
comes so oxidated that a scale of considerable thick- 
ness peels off, and with this scale part of the car- 
bon is extracted from the surface of the steel, and, if 
the temperature of the steel is still further increased, 
its affinity for oxygen is also increased, and when 
approaching the point of fusion the affinity becomes 
very strong, and the combustion is, consequently, 
rapid ; and at a melting heat, in the presence of a 
large quantity of oxygen, the carbon cannot exist in 
the steel — at least, only for a very short time. If 
further proof than this be required, the reader has 
only to consult the process of Mr. Bessemer in man- 
ufacturing steel or malleable iron direct from the 
cast iron. Steel which has been slightly overheated 
may be restored in a slight degree by giving it a 
judicious hammering at a lowered heat. This will, 
however, improve burnt steel but little, though the 
hammering will make the steel denser ; yet no de- 
gree of heat or hammering will restore to steel the 
carbon or the original fineness of texture of which 

it has been deprived by being overheated. 
3* 



1 



58 FOKGLNG AND WELDING IKON AND STEEL. 

The heat steel receives in forging must also, like 
the heat of iron, be judged by the eye ; and the 
temperature suitable differs in some degree with its 
quality and mode of manufacture : the heat required, 
diminishes with the increase of carbon. Thus steel 
equires much more precaution as to the degree of 
heat than iron, and does not bear the same degree of 
heat as iron without injury ; but it will bear a much 
greater amount of hardship under the hammer than 
iron if it is cautiously heated. 

Steel requires to be heated more slowly than iron? 
and requires more moving about in the fire in order 
to equalize the heat and to receive a uniform temper- 
ature throughout ; it requires also to be drawn from 
the fire more frequently, as it requires to be well 
watched to heat it properly. 

The tenacity of steel hammered at a low heat 
is considerably increased ; and, in forging cutting- 
tools, the hammering should be applied in the most 
equal manner throughout, and should be continued 
until nearly cold. But the effect of the hammering 
is taken off again, if the steel is heated to a high 
degree. When forging cold chisels, they ought al- 
ways to be finished with the flatter ; and they will 
stand better if the last blows are given upon their 
flat sides. 

The elasticity of iron and of steel hammered cold 
is considerably increased— that is, providing the 
hammering is not carried to an extreme. Bell- 
springs are sometimes made of sheet steel, and very 
frequently of hoop iron thus managed : straight- 
edges, and the blades of squares as they are sold at 



FORGING AND WELDING IKON AND STEEL. 



59 



the ironmongers' shops, are sometimes made of tem- 
pered steel. But they are more frequently made 
of sheet steel hammered cold, and they are not un- 
frequently made of hoop iron thus managed. 

To change the form of iron when it is not neces- 
sary to weld it, the white-name heat is used ; and, 
according to the size of the work, it is battered by 
one, two, or more men with sledge-hammers. The 
hammers are generally slung entirely round, with 
both hands, and held nearly at the end of the handle ; 
they are generally directed to fall upon the work at 
the centre of the anvil, and the work is gradually 
moved backward and forward to expose the re- 
quired parts to the action of the hammers. Two 
gangs of men are sometimes required for the larger 
work done at the common forge ; they relieve each 
other at intervals, as the work is very laborious. 
When the iron is nearly reduced to the required 
shape and size, the strength of the blows is reduced, 
and the hammers are made to fall upon the work 
as nearly flat as possible, in order to smooth the 
work after which, the flatter or the swage-tool is 
held upon the work, and the blows of the ham- 
mers are directed upon the head of the tools to finish 
off the work, the dexterous use of which saves 

filing. 

much trouble in the after-processes of chipping and 
When it is required to thicken any part of a bar 
of iron without welding, the operation called upset- 
ting must be resorted to. This consists in giving it 
the white-flame heat at the part to be thickened, 
and, while one end rests upon the anvil, hammering 



60 FORGING AND WELDING IRON AND STEEL. 

at the other till the required size is produced 
When the bar is large, if it be lifted and jumped 
upon the anvil, or upon a lump of iron placed upon 
the floor, its own weight will supply the required 
force for upsetting it. 

"When it is required to weld two bars of iron to- 
gether, the sparkling or welding heat is used. The 
ends are first upset or made thicker by jumping 
them endways upon the anvil ; each end is then 
bevelled off to a thin edge (called scarfing) ; the two 
ends are then placed in the fire, and raised to a 
welding heat, or nearly to a state of fusion : care is 
required that both arrive at the proper heat at the 
same time. The bars may in part be prevented from 
wasting by taking care to supply them at the heated 
part with powdered glass or sand just . before they 
arrive at the welding heat ; the sand or other material 
melts on the surface of the iron, and serves to form a 
flux or fluid glass which protects the iron from the 
impurities of the fuel and defends it from the air, at 
the same time uniting with and removing the oxide 
which may have been formed on the heated scarfs, 
the removal of which greatly facilitates the opera- 
tion of welding. 

When the two bars of iron to be united have at- 
tained the welding heat, they are taken out of the 
fire with the utmost dispatch ; a good portion of 
the scale or dirt which would hinder their uniting is 
got rid of by striking the bars across the anvil : they 
are then placed in contact at the heated part, and 
hammered until no visible seam or fissure remains. 
If they have not been sufficiently united, the heat- 



EOKGING AND WELDING IRON AND STEEL. 61 

irig and hammering ought to be repeated until the 
work is perfectly sound. 

The larger bars, such as heavy shafts for machine- 
ry, are generally part welded within the fire; the 
two ends are prepared so that one fits within the 
other (called the split joint) ; a Y piece is cut out 
of the end of one bar with the chisel, and the end 
of the other bar is cut so as to fit into it ; when the 
ends are properly fitted, they are placed in their 
proper positions in the fire, and when they arrive at 
the proper heat they are welded together by striking 
the end of one of the bars with the sledge-hammers? 
or by striking with some other contrivance, such as 
by a mass of iron suspended by a chain from the 
ceiling, while several men hold against the opposite 
bar to sustain the blows. .This contrivance is far 
more effective thau the blows of the sledge-hammer, 
more especially when a thick lump of iron is placed 
against the opposite end : the heat is kept np all the 
time, and the whole is afterward lifted from the 
fire, and finished upon the anvil. The amount of 
labor saved by this kind of joint for large works, in 
comparison with the scarf joint, is considerable ; and 
it is probably the most effectual way of getting a 
sound joint. 

When a thick lump is required on the end of a 
bar, it is frequently made by cutting the iron partly 
through in several places, and doubling it backward 
and forward according to the thickness required ; 
the whole is then welded into a solid mass. Ilam- 
mers are frequently made from the iron thus man- 
aged, as the iron is less liable to split than the 



62 FORGING AND WELDING IRON AND STEEL. 

plain bar of iron in punching the eye. Sometimes 
the iron is prepared for making a hammer, by weld- 
ing a collar (made of a flat bar) round a bar of round 
iron ; at other times a flat bar is heated at the end 
and rolled up similar to a roll of ribbon, and after- 
ward welded into a solid lump. 

When a very thick lump is required on the centre 
of a long bar of iron, the method of drawing the two 
ends down from a large bar would be too expensive ; 
the method of upsetting the bar would be impracti- 
cable, consequently a large collar is welded round 
the middle. But as there is great difficulty in get- 
ting a very wide collar soundly welded upon the 
bar, two collars half the width of the single collar 
are placed close together and welded upon the bar ; 
the two collars give the bar a better opportunity of 
attaining the welding; heat, and the union is made 
perfect. 

Sometimes a large collar is made upon a bar 
of iron by three or four pieces of a flat bar, heat- 
ed and welded on separately ; and this is proba- 
bly the most effectual way of getting a very large 
collar upon the bar. It is obvious that the method 
of drawing the two ends down from a large bar will 
produce the soundest work (providing the bar itself 
be sound) ; but then, as I have just remarked, with 
very long bars it would be very expensive. When 
a very large steel collar is required to be welded on 
to a bar of iron, it becomes absolutely necessary to 
weld it on in pieces ; because, from the greater fusi- 
bility of the steel, it is quite impracticable to weld 
a very wide steel collar (made in one piece) upon a 



FOKGLNG- AND WELDING IKON AND STEEL. 63 

bar of iron, for the steel will burn before the iron 
enclosed in it can attain the welding heat. 

It is well known to practical men that a collar 
made from very fusible impure iron can never be 
effectually welded upon a bar of pure fibrous iron, 
because an impure iron, from its greater fusibility, 
will not stand the heat which is suitable to weld 
pure fibrous iron ; consequently, when a piece of a 
pure fibrous iron is enclosed in a collar made of an 
impure fusible iron, the impure iron must burn 
before the pure fibrous iron can attain the heat suit- 
able to weld its own material ; besides, a pure fibrous 
iron requires a flux to be applied to it just before it 
arrives at the welding heat, while an impure iron 
forms a flux or slag from its own material ; and, as 
an impure iron burns at a heat which is not sufficient 
to weld pure fibrous iron, it forms a slag between the 
two irons and hinders their incorporation. Again, 
if the two different irons were heated at different 
temperatures suitable to both, they could not even 
then be effectually welded together because the force 
of the blows requisite to weld pure fibrous iron will 
disperse fusible impure iron. It is evident, then, 
that if there is great difficulty in welding a collar 
made of an impure iron upon a bar of pure fibrous 
iron, that there will be still greater difficulty in 
welding a large steel collar (made in a single piece) 
upon a bar of iron ; therefore, when a very large 
steel collar is required upon a bar of iron, it becomes 
absolutely necessary to weld it on in separate pieces. 

To weld steel to steel, then, or steel to iron, with- 
out injuring the steel, is an operation which demands 



64 FORGING AND WELDING IRON AND STEEL. 

great nicety of management, as there are a variety 
of degrees of heat to deal with. The welding heat 
of steel is lower than that of iron, from its greater 
fusibility ; and the more fusible the steel the less 
easily it welds. Highly carbonized cast steel (tool 
steel) welds with greater difficulty than mild cast 
steel, which contains a smaller proportion of carbon ; 
although mild cast steel is superior in its welding 
properties to highly carbonized cast steel, still it 
is inferior in its hardening properties. The steel 
which contains the smallest proportion of carbon, 
and which has the most fibrous texture, — as, for 
example, the double shear steel, — is the most easily 
welded ; for, it having been most wrought by the 
hammer, or between the rollers, its fibrous character 
is partly restored. 

Cast steel is the most difficult to weld, on account 
of its having been in a state of fusion, which entire- 
ly destroys its fibrous texture. 

The material (sand) which is used to serve as a 
flux to protect and fit good iron for welding does 
not answer well for steel, because it is too refracto- 
ry ; and some kinds of cast steel burn or melt at a 
lower heat than sand, consequently the sand would 
be useless to serve as a flux. 

The material used to serve as a flux for welding 
blister and shear steel is generally powdered borax, 
though sand is frequently used. But ordinary cast 
steel, from its greater fusibility, requires a still more 
fusible flux, and, for this purpose, sal ammoniac is 
mixed with the borax. 

The borax of commerce, as sold by chemists, is 



FORGING AND WELDING IRON AND STEEL. 65 

composed of a very large proportion of water ; con- 
sequently it requires to be put into an iron or other 
suitable vessel and boiled over the fire till all the 
water is expelled, after which it requires to be 
ground to powder before it is used. When it is re- 
quired to mix sal ammoniac with borax, the propor- 
tions are about sixteen parts of the borax to one of 
sal ammoniac. 

The material used to serve as a flux for steel must 
be suitable to protect it, at the same time purify the 
surface ; and should always be applied just before 
the metal reaches the welding heat, no matter how 
high or low that heat may be. 

"When it is required to weld two bars of blister 
or shear steel together, they are heated at the ends 
and upset or made thicker, and afterward scarfed 
the same way as iron bars for welding ; the two 
ends are then heated^ to a moderate white heat and 
sprinkled with borax; the temperature is then 
raised to the proper welding heat suitable to the 
steel. Care is required that both arrive at the 
proper heat at the same moment, after which they 
are taken from the fire to the anvil and hammered 
till no visible seam remains. 

When it is required to weld two large bars of 
cast steel together, which are not too highly carbon- 
ized, they are first heated at the ends and upset, and 
scarfed the same way as other bars for welding, with 
the exception that a thin cutter-hole is punched in 
the scarfed ends of the cast-steel bars for riveting: 
them together previous to welding. 

Cast steel will not admit of being; made so soft 



66 FORGING AND WELDING IEON AND STEEL. 

in the fire as iron or the other kinds of steel ; con- 
sequently, when it is first struck with the hammers, 
the scarfs are more liable to slip off each other ; and 
it is to guard against this inconvenience that the 
bars are riveted together, and not with the view of 
gaining strength in the joint, as might be imagined. 
When the bars are riveted together, the joint is 
placed in a bright, clean, and close fire, the steel is 
heated as high as it will bear without much injury, 
or as hot as can be done with safety ; the material 
to serve as a welding powder or flux (calcined borax 
and sal ammoniac) is then put on the heated scarfs, 
after which the steel is carefully turned over in the 
fire and supplied with more of the powder. It is 
not necessary to draw the steel out of the fire to 
put the powder on, as the powder may be spread on 
the heated scarfs by a slip of sheet iron, the end of 
which requires to be made like a spoon ; but, whilst 
in the act of spreading the powder upon the steel, 
the blast must be sparingly used, or it would blow 
the powder from off the spoon, and it would be 
wasted in the fire. 

The sal ammoniac cleans the dirt from the steel, 
and the borax causes it to fuse before it attains that 
heat which will burn the steel ; and when at the 
point of fusion it is lifted from the fire to the anvil 
and hammered and welded much in the same man- 
ner as other kinds of steel or iron. The blows are 
given gently at first, owing to the weak state the 
steel is in by the lessening of its cohesion by the 
heat. But as the cohesion of the steel increases, 
the strength of the blows is increased also ; if the 



FORGING AND WELDING TRON AND STEEL. 67 

bars are not sufficiently united, the heating and 
hammering must be repeated until the joint is per- 
fectly sound. 

When it is required to weld steel to iron, the 
steel must be heated in a less degree than the iron, 
consequently they ought to bo heated separately ; 
and, when they arrive at the welding temperature 
suitable to both, they must be brought to the anvil, 
the dirt which would hinder their incorporation 
must be brushed off, they must then be placed in 
contact with each other at the heated parts and 
united by hammering. Should there happen to be 
any defective part in the weld, the heating and 
hammering must be repeated, taking care in the 
second heating (as far as is practicable) to keep the 
iron facing the hottest part of the fire, or the steel 
is liable to be injured. 

When a large quantity of steel is required to be 
cut down into suitable lengths for screw-taps, or 
similar articles, it is generally the smith who is ap- 
pointed to cut it to the required lengths ; and, 
whilst in the smithy, perhaps a few words upon the 
cutting of cold steel with the cold chisel, will not 
be out of place. I was once working for an em- 
ployer who had a large order for screw-taps, and I 
was appointed to cut the steel into lengths with the 
rod cold chisel (a short thick chisel with a hazel- 
stick twisted round it to form the handle); but, 
previous to commencing to cut the steel, my em- 
ployer informed me that he did not much approve 
of cutting the steel down into lengths with the cold 
chisel, as he had discovered a fracture in a large 



G$ FOKGLNG AND WELDING IRON AND STEEL. 

number of his taps which he had previously hard- 
ened, and, as this fracture was at the end of the 
taps, he was inclined to think that it was caused in 
the cutting and breaking down of the steel. Being 
myself rather inquisitive in such matters, I closely 
examined the taps, and found that the fracture was 
not caused by the cutting and breaking down of the 
steel, but by boring the centres too large and too 
deep. Though the fracture in this instance was not 
caused at the time of the breaking down of the 
steel, still, it very frequently happens, that an in- 
ternal fracture is caused in the steel in cutting 
and breaking it into lengths, especially when the 
steel is nicked with a dull or blunt chisel ; and the 
fracture will not at all times be visible until after 
the steel is hardened ; but after it is hardened it 
can readily be detected. As a remedy to prevent 
this fracture, I would advise those who cut their 
steel down into lengths with the cold chisel, always 
to keep a good sharp edge upon the chisel and nick 
the steel all round, instead of only upon the two 
opposite sides as is often done. The steel will then 
break easier and be less liable to splinter on the 
outside, and less liable to fracture inside. 

"When the steel is too large to be conveniently 
cut and broken cold, it will sometimes be more 
economical to heat the steel to a red heat before 
cutting it ; sometimes it will be more economical to 
cut it into lengths in the turning-lathe by means of 
an instrument called a parting-tool. 

Steel is sometimes heated and sawn into lengths 
by means of a circular saw driven by machinery, 



FORGING AND WELDING IRON AND STEEL. 69 

but this is far from being the best method for cut- 
ting the best kinds of cast steel. 

Most workmen when cutting steel down into 
lengths with the cold chisel, adopt one or other of 
the following methods : they first nick the steel 
with the chisel, and then lay the cut across the 
square hole of the anvil, in order that the steel may 
lie hollow, and then strike it with the pane of the 
sledge-hammer ; sometimes the chisel is held in the 
nick, while the nick lies across the hole of the an- 
vil, and the blows of the hammer directed upon the 
chisel ; the steel is sometimes made to lie hollow by 
laying it across the anvil, at the same time holding 
a rod of iron (generally the poker) beneath it near 
to the nick, and then break it by striking with the 
sledge-hammer, the blows of the hammer being di- 
rected upon the nick ; sometimes the steel is broken 
by first nicking it with the chisel as before, and 
then striking; the bar across the beak-iron of the 
anvil. 

It may, perhaps, be thought by some, that there 
was no necessity for speaking upon these simple 
methods of cutting and breaking steel into lengths ; 
but I have thought it necessary to notice them, on 
account of having witnessed very serious accidents 
happen by adopting these methods, by the steel 
flying and striking workmen who happened to be 
working near where steel was being cut and broken. 
In my opinion any contrivance, or any hint which 
may have a tendency to prevent accidents, cannot 
be useless. 

When it is necessary to cut a large quantity of 



70 FORGING AND WELDING IRON AND STEEL. 

steel into lengths with the cold chisel, and where a 
number of workmen are at work, a piece of tem- 
porary boarding ought always to be placed in front 
of the anvil, at about two or three yards distant 
from the anvil ; the chisel should be sharp, and also 
properly well secured to the handle, as accidents 
have happened from the neglect of this. The 
striker ought not to stand in front of the steel, as it 
is very dangerous to do so ; but he should stand 
rather on one side, for, if the steel is very hard, it 
will sometimes unexpectedly break with the first or 
second cut of the chisel. The steel ought not to be 
laid across the hole of the anvil to break it, as this 
is a very dangerous practice (although frequently 
adopted). A better plan is, after the steel has been 
nicked on all sides with the chisel, to place the 
swage-block upon its edge, and then put the steel 
through one of the holes, the piece of steel to be 
broken being allowed to project through the hole. 
It may then be broken off with a very light blow 
of the hammer, and the piece of steel will drop 
clown close to the swage-block. If these methods 
be strictly adhered to, many a serious accident will 
be prevented. 



CHAPTER V. 

ANNEALING OF OAST IRON AND STEEL. 

Thebe are many substances which, when rapidly 
cooled after having been heated, become hard and 
brittle. Glass, cast iron, and steel possess this pe- 
culiarity. Although hardness (as will subsequently 
be shown) is such a useful and important property 
in steel, still, when steel becomes hard in the pro- 
cess of manufacture, or in the process of forging it 
into various kinds of articles, the hardness becomes 
then an inconvenience, at least when the articles 
require to be turned, engraved upon, filed, or 
screwed ; and the only remedy for removing this 
inconvenience is to reheat the steel, and allow it to 
cool very gradually. This process is called anneal- 
ing. Glass vessels are generally annealed by per- 
mitting them to cool very gradually in longer or 
shorter time, according to their thickness and bulk, 
in an oven constructed for the purpose. Steel is 
annealed in a variety of ways. Some artists anneal 
steel by heating it to redness in the open or hollow 
fire, and then burying it in lime ; others heat it 
and bury it in sand ; others heat it and bury it in 
cast-iron borings ; others heat it and bury it in*dry 
sawdust, and some anneal it by surrounding it on 
all sides in an iron box, with carbon, and then heat 



72 ANNEALING OF CAST IRON AND STEEL. 

the whole to redness. This latter process is un- 
doubtedly the most effectual method of annealing 
steel ; that is, providing the steel is not heated to 
excess. When this method of annealing steel is 
adopted, a layer of wood charcoal, coarsely pow- 
dered, is placed at the bottom of an iron box, and 
then a layer of the steel, upon this another layer of 
charcoal, and upon that again another layer of 
steel, and so on until the box is nearly full, finish- 
ing with a layer of charcoal. The lid of the box 
must then be put on, and the box luted with clay 
or loam, in order to exclude the air. The whole 
may then be placed in a furnace or hollow fire, and 
gradually heated to redness. The size and shape 
of the box, it is obvious, must vary with the shape 
and quantity of the steel requiring to be operated 
upon. It must be borne in mind that the same care 
is required in heating the steel in this process as 
there is in heating the steel for forging or harden- 
ing. Overheating the steel in any one of the pro- 
cesses is hurtful. It is seldom necessary to keep up 
the heat beyond the time that the contents of the 
box are uniformly heated, unless the steel should 
happen to contain particles of hard impure iron, 
when it would then be necessary to keep up the 
heat for several hours. "When the whole has ar- 
rived at the proper temperature the box may then 
be withdrawn from the fire and buried in some hot 
or cold ashes to become quite cool, or may be left 
in flie fire, and the fire allowed to cool down. It 
is quite necessary, however, that the steel should be 
protected from air until it becomes cool. After be- 



■ ANNEALING OF CAST IRON AND STEEL. 73 

coming cool, and being taken out of the box, it is 
then in a fit state for the fitting or turning room. 
The steel will then be very soft and free from those 
hard bright spots which workmen call pins, and 
which are impediments to the filing and turning of 
steel. If the steel and the charcoal have been prop- 
erly protected from the air, the surface of the steel 
will be as free from oxidation as it was before it 
was heated, and the greater portion of the charcoal 
will remain unconsumecl, as it has been preserved 
from combustion ; consequently it has undergone 
little change, with the exception of being hardened, 
and its color changed to a deeper black. It can 
therefore be put aside to be used again. This mode 
of annealing prevents the steel from losing any of 
its quality ; but the steel absorbs by the process a 
small quantity of carbon, which is favorable to the 
steel in the hardening process, which will be ex- 
plained in the chapter upon the hardening of steel. 
It may be well to state that animal charcoal is some- 
times used as well as wood charcoal for annealing. 

Less than a certain heat will fail to make steel 
hard, but, on the contrary, will soften it ; and some- 
times this effect is useful. For instance, suppose a 
piece of steel (for any special pnrpose) is wanted in 
a hurry, and suppose the steel has become by ham- 
mering too hard to be dressed with the file, or cut 
with the turning-tool, and time will not admit of 
its being softened in a box with charcoal powder 
the steel may be heated to a cherry-red heat in an 
open fire, then be drawn out of the fire, and allowed 
to cool down till the red heat is not visible by day- 



74 ANNEALING OF CAST IRON AND STEEL. 

light, but can be seen in a dark place beneath or 
behind the forge, then to be plunged at this heat 
into cold water, and allowed to remain in the water 
until it becomes quite cool. When taken out of 
the water it will be found to be more uniform in 
temper than when it left the forge ; consequently 
it will work more pleasantly with the file or the 
turning-tool. This is a very expeditious way of an- 
nealing steel ; but the steel will not be quite so soft 
as steel which is enclosed in the iron box, and an- 
nealed in contact with charcoal powder. 

There are many who do not know the value of 
a good tool because the steel they work upon has 
not been properly annealed, and before the tool has 
half done its duty it is either worn out or wants re- 
pairing; whereas, if the steel had been properly 
annealed, the same tool would have lasted very 
much longer without needing repair. Steel re- 
quired to be annealed in such large quantities as to 
make it inconvenient, or the expense of enclosing it 
in boxes too great, may be heated in a charcoal fire 
completely enveloped and protected from the air. 
After the steel has become heated to the proper 
temperature, the fire and the steel may be covered 
over with pieces of plate iron. The whole may 
then be covered over with cinder-ashes and the fire 
allowed to go out of its own accord. It will thus 
be protected until it is cold. Charcoal, especially 
when it is used as fuel in the open fire, is consumed 
with rapidity, and therefore very expensive. The 
steel may, however, be heated in a cinder fire, 
Avliich is less expensive in the cost of an equal 



' ANNEALING OF CAST IKON AND STEEL. 75 

measure and also in the rate of its consumption. 
This kind of fuel is not so pure as charcoal, but it 
is purer than coal, and affords a very moderate 
heat. When the steel is at the proper heat it must 
be taken out of the cinder fire and placed in an iron 
box containing coarsely powdered charcoal; the 
charcoal must completely envelop the steel, and the- 
box will require to be covered up and luted with 
clay or loam, in order to exclude the air and pre- 
serve the charcoal for future use. 

Cast iron may be annealed in a similar manner 
as steel. Cast iron in the state it leaves the moulds 
is always surrounded with a crust or coating, some- 
thing similar to the coating of steel which surrounds 
case-hardened iron ; and this coating is sometimes so 
extremely hard that the best file or turning-tool will 
make no impression upon it, while the interior of 
the casting is soft and manageable. This hard crust 
is generally removed by the workmen either by chip- 
ping it with the cold chisel, or by grinding it on a 
large grin ding-stone, turned by machinery. But 
when the shape of the casting is such that this crust 
cannot conveniently be removed with the chisel or 
the grin ding-stone, annealing then is the most eco- 
nomical process, as it makes the whole casting soft 
and much easier to work, but still does not deprive 
it of its natural character. 

To anneal cast iron the heat requires to be kept 
up much longer than for steel. Cast iron requires to 
have solid supports to keep it from bending or break- 
ing by the heat. Cast iron, like steel, when annealed, 
is more uniform in temper ; consequently it is less 



70 ANNEALING OF CAST IKON AND STEEL. 

liable to alter its figure by a subsequent partial expo- 
sure to moderate beat, than that which has not been 
annealed. 

The outside of cast iron, even when it is annealed, 
is always somewhat harder than the internal part, 
unless such processes be adopted as will abstract the 
carbon from the exterior part ; but these processes, 
it is obvious, deprive it of its natural character and 
make it in the condition of malleable iron, but 
without the fibre which is due to the hammering 
and rolling. Cast-iron cutlery is enclosed in boxes 
and cemented with some substance containing oxy- 
gen, such as poor iron ores free from sulphur, the 
scales from the smith's anvil, and various other ab- 
sorbents of carbon. The boxes are luted in a simi- 
lar manner as the boxes when annealing steel or 
case-hardening iron ; they are afterward placed in 
suitable furnaces and the cast articles are kept in a 
state little short of fusion for two or three days ; 
they are then founj^o possess a considerable degree 
of malleability, and can be readily bent and slightly 
forged. Copper forms an exception to the general 
rule of annealing; copper is actually made softer 
and more flexible by plunging it when red hot into 
cold water, than by any other means. The gradual 
cooling of copper in a similar manner as steel or 
cast iron produces a contrary effect. When copper is 
required very soft and the surface very clean, a 
small quantity of sulphuric acid (vitriol) may be put 
into the water, which will have the effect of remov- 
ing all the black scale from its surface. 



CHAPTER VI. 

HARDENING AND TEMPERING OF STEEL. 

TVe have now arrived at a very important pro- 
cess, justly termed the crowning process. It is that of 
hardening the articles ; and, if the proper steel has 
not been chosen for the articles, or if the proper steel 
has been chosen and has not afterward been properly 
treated through all the stages which it has had to pass, 
or if the hardener be not fully aware of the general 
principles upon which he must proceed, all past 
efforts may prove futile. It is not requisite that the 
hardener should be a chemist ; but some slight ac- 
quaintance at least with chemistry, or of the action 
of substances upon each other, will be extremely 
serviceable to him. To be unqualified in this re- 
spect will be laboring in the dark : a successful re- 
sult may often be obtained ; but it will be very im- 
perfectly known how it happened, and it will afford 
no valuable instruction for the future. 

There are too many who entertain an opinion 
that they have nothing new to learn which is worth 
notice; they are apt, in effect, to say, that, having 
served an apprenticeship to their business, they ought 
to know something, and because they ought to know 
something, they seem to expect submission to their 
very errors. To such I speak not ; to convince them 



78 HARDENING AND. TEMPERING OF STEEL. 

would be impossible, and therefore the attempt folly. 
But the prudent artisan, whose first care is generally 
to provide himself with tools adapted to his labors, 
I would ask to improve his knowledge of that ma- 
terial, the proper choice and management of which 
constitutes the first step toward success in mechan- 
ical pursuits. 

The art of hardening and tempering steel con- 
stitutes one of the most delicate, curious, and useful 
branches connected with mechanical art ; it is an art 
of long standing, and always one of anxiety, but 
by whom or when it was first adopted I am not pre- 
pared to decide. In this place it claims notice on 
account of its contributing so essentially to the per- 
fection of all the other arts. The great steam-en- 
gines, iron bridges, Atlantic cables, and iron ships 
of the present day, are much indebted to this branch 
of art ; and without it the six hundred-pounder guns, 
or even the Great Exhibition itself, might never 
have been seen. A proper inquiry, therefore, into 
this delicate branch of art must prove very useful 
to the engineer, as well as to the young beginner, 
and may not prove uninteresting even to the gen- 
eral reader, especially when processes which do not 
generally appear, and are not often communicated 
by workmen, are explained. At first sight the art 
of hardening and tempering steel appears sufficient- 
ly simple, when by heating a piece of steel to red- 
ness, and plunging it into cold water, it becomes 
hard ; on a closer inspection, however, the mind will 
soon discover that many operations and contrivances 
require to be carried into effect by the hardener in 



■HARDENING AND TEMPERING OP STEEL. 79 

order to become efficient in his art, or to be distin- 
guished for skill and promptitude in execution. A 
slight knowledge of the processes will also discover 
that a certain amount of patient perseverance is 
required — an amount of which few who have been 
brought up at the desk, or behind the counter, can 
form the slightest idea. But I have not set out with 
the object to discourage the young practitioner, but 
rather to encourage him and smooth for him the 
path which I have myself found so rough, but which 
I have always endeavored to explore without enter- 
taining a sentiment of its hardship ; and I would 
advise all young men who are just starting in the 
world to go and do likewise-. 

Before proceeding further, I would state, that I 
have not undertaken to explain every thing in con- 
nection with this subject ; but my main object in the 
present chapter is to explain, in a plain way, the 
chief causes why steel breaks in hardening ; also to 
notice some of the contrivances which I have found 
in my own experience to be the least expensive, and 
most easily reducible to practice ; the most suitable 
to prevent steel from breaking ; and, if the informa- 
tion be properly studied, it will enable the mechanic 
to harden and temper any kind of arftcle with which 
he may have to do. 

Many theories upon the cause of steel becoming 
hard by the process of heating and suddenly cooling 
it have been formed ; but they are so beset with diffi- 
culties and uncertainty, that in my opinion the prop- 
er cause has not yet been proved. I have previous- 
ly shown that steel is a compound of iron and carbon ; 



80 HARDENING AND TEMPERING OF STEEL. 

and, as pure iron does not harden by simple immer- 
sion, it must be to its carbon that steel owes this 
valuable property; and, if I may be allowed to 
theorize on the reason why steel becomes hard by 
sudden cooling, I should be inclined to state that it 
is the crystallization of the carbon, caused by com- 
pression and sudden cooling, and, being combined 
with the iron, becomes a hard and solid substance ; 
but, let this be so or not, there is one thing certain, 
that a new arrangement of the particles takes place 
by the process of hardening. But, as I shall have 
an occasion to speak upon this hereafter (in the chap- 
ter upon the expansion and contraction of steel), it 
will be superfluous to speak upon it in this place, 
but rather confine myself to the mechanical opera- 
tions of the subject. 

It is of considerable importance that the designer 
of tools or other articles should have some knowledge 
of the quality of the material to be used ; likewise 
he should have some knowledge of the action of 
fire and water upon the material; also he should 
have some knowledge of the practice of the hard- 
ener. 

The workmen, through whose hands the articles 
must pass, either in the fitting or the turning room, 
should also have some knowledge of the art of hard- 
ening ; in fact, it is as requisite that fitters and turn- 
ers should have some knowledge of the practice of 
the hardener and the action of fire and water upon 
the steel, as it is for the pattern-maker to have some 
knowledge of the practice of the moulder. 

The superior character of castings depends in a 



• HARDENING AND TEMPERING OF STEEL. 81 

great measure upon the superior skill which has 
been displayed upon the patterns ; and the success in 
the hardening of steel, in many instances, depends 
in a great measure upon the ingenuity displayed in 
the fitting or the turning room, and also on the in- 
genuity displayed in designing the article. 

Too little attention is generally paid to the 
quality of the material when required for very par- 
ticular tools, or, in other words, for tools that require 
a great amount of labor and time to make them ; 
and in the fitting or the turning room, or even in 
the drawing-office, the expansion and contraction 
of steel is seldom heeded or even thought of, though 
it is of the greatest importance. 

When it is required to make an expensive article, 
and where there is great risk of its breaking in the 
hardening, the first thing to be done is to select the 
proper steel for the purpose and afterward to an- 
neal it to the fullest extent ; if an equal and judi- 
cious hammering be given to the steel by the smith 
before it is annealed it gives a density to the steel 
and the article will be more durable ; besides, it 
will lessen the risk of its breaking in the hardening, 
but the effect of the hammering, as I have before 
remarked, is taken off again by strong ignition, and 
the smith's labor is lost, therefore it is evident that 
there is as much care required in heating the steel 
when it is required to be annealed as there is in 
heating it when it is required to be forged or hard- 
ened. When the steel is annealed it is then in a fit 
state for the fitting or the turning room, there to be 
fashioned into the required article. 
4* 



82 HARDENING AND TEMPERING OF STEEL. 

The artist employed upon it ought to bear in 
mind that steel breaks in hardening from its unequal 
contraction at different parts ; the danger increases 
with the thickness and bulk, and the more especially 
when certain parts are unequally thick and thin, 
consequently before finishing any article for hard- 
ening one thing should be attended to, which I will 
attempt to explain, and, if I succeed in making it 
understood, the artist will have obtained information 
as to the plans to be adopted with large articles 
generally. It is this : examine the article and see 
which part of it is likely to be the last to become 
cold when it is immersed in the water, and if it is 
practicable to reduce the steel in that part without 
inconveniencing the article it is advisable to do so ; 
the steel will then cool more uuiformly and be less 
liable to fracture. If it were possible to get every 
particle of the steel cold at the same moment, there 
would be an end to the danger of steel breaking in 
hardening ; but, as this cannot be done, we must 
approach it as near as we can. 

For the better understanding of the subject, let 
us suppose that a large circular cutter, such as are 
used for shaping and trueing of work of various 
shapes, is required to be made, we will suppose it 
to be required about seven inches in diameter and 
two inches in thickness, with numerous cutting- 
edges (termed teeth) round the circumference, and 
a round hole in the centre through which to pass 
the spindle. It is obvious that the first thing which 
will require to be done will be to select the proper 
steel for the cutter and afterward to forge it to the 



HARDENING- AND TEMPERING OF STEEL. 83 

required dimensions, after which it will require to 
be annealed to the fullest extent ; but as the choos- 
ing, forging, and annealing have already been 
treated of, it will be superfluous to speak more upon 
it in this place, consequently, let us suppose the 
steel in its forged and annealed state to be obtained. 
The ftrst thing usually clone after the steel is ob- 
tained is to bore the mandrel-hole, after which it is 
turned to the required thickness, and the two sides 
of the block of steel left; flat ; the superfluous metal 
upon the circumference is then turned off, which 
leaves the block of the required diameter. The 
teeth are now cut upon the circumference of this 
block of steel, either by means of a file or by a tool 
whose edge is of the proper form, and can be used 
either in a planing or shaping machine, or even 
with the lathe. But the most perfect teeth are cut 
by means of another rotary cutter, whose edge is 
of the proper form, and working in a machine con- 
structed for the purpose. It is usual to bore the 
mandrel-hole in large cutters, the same size as the 
mandrel-hole in the smaller size cutters, so that 
both large and middle size cutters may fit the same 
mandrel, but this is a step in a wrong direction. 
The larger the cutter the larger the mandrel-hole 
should be — not to say that the mandrel itself would 
not be strong enough ; but a large mandrel-hole in 
large cutters favors the cutters in hardening by al- 
lowing the steel to cool more uniformly ; whereas 
a small mandrel-hole in a large cutter, having two 
plain flat sides or surfaces, increases the risk of the 
cutter breaking in hardening!;, Though a large 



84: HARDENING AND TEMPERING OF STEEL. 

mandrel-hole favors a large cutter in hardening, 
still it is not absolutely necessary to have a large 
mandrel-hole in them, because large cutters having 
a small inandrel-hole in them may be hardened 
without breaking them, by taking care previou s to 
hardening them to reduce the substance of the 
steel. • * 

The substance of the steel must be reduced in that 
part of the cutter which is the last to become cool 
when it is immersed in the water. It is obvious 
that the part which is the last to become cold will 
be half way between the mandrel-hole and the cir- 
cumference, consequently large cutters will require 
to be dished out or turned concave on both sides ; 
or if a few smaller holes than the mandrel-hole be 
bored round the mandrel-hole, it will answer the 
same purpose as turning each side concave. Either 
of the above plans will greatly reduce the risk of 
all large cutters breaking in hardening, and it does 
not materially reduce their strength or stability. 

It is obvious that the method of turning the 
sides of large cutters concave cannot be adopted 
with cutters which require to have teeth on their 
sides as well as on their circumference ; still holes 
could be bored through these, and probably it 
would not in the least prevent the cutter from 
doing its work ; still the cutter would not have a 
very pleasing appearance, and it would not look 
very mechanical. Consequently, instead of boring 
holes in these kinds of large cutters, it will be 
better to make the mandrel-hole large in propor- 
tion to the cutter. 



HAEDENING AND TEMPEKESTG OF STEEL. 85 

Perhaps it will be of some use to hint, as it is a 
very valuable hint if properly taken, that a circular 
cutter of any required thickness, and seveu inches 
in diameter, and which has a three-inch mandrel- 
hole through its centre, is less liable to break in 
hardening than a circular cutter of the same thick- 
ness, six inches in diameter, and which has a two- 
inch mandrel-hole through its centre. 

There are numbers of articles besides cutters 
which require to be hardened, where it becomes 
necessary to bore holes in them, or cut out a kind of 
panel to make them cool more equally. In some 
instances boring holes in steel articles requiring to 
be hardened is injurious or unfavorable to the arti- 
cles in hardening. For instance, boring holes too 
near the outside edges of some kinds of articles will 
sometimes cause the article to crack at the hole. 

It may be well to state that drilling a hole or 
centre too large or too deep into screw-taps or ri- 
mers, and various other articles which require to be 
hardened, is a great evil and should in general be 
avoided ; for, when the centres are too large or too 
deep, it weakens the ends of the articles, and it not 
only weakens the ends of the articles, but it fre- 
quently causes a fracture in the steel at the bottom 
of the centre. 

In all cases, if the centres are not required in the 
articles after they are hardened, it is advisable to file 
them oiit previous to hardening them, and thus pre- 
vent all risk of their getting cracked at that part in 
hardening. 

In making steel tools or steel articles of any de- 



86 HARDENING AND TEMPERING OF STEEL. 

scription sharp internal angles should in general be 
avoided, as they are very unfavorable in the hard- 
ening process ; consequently the key-ways in cutters 
should be half circle. In all kinds of articles sharp 
internal angles are unfavorable to the strength of 
the articles, so that it becomes necessary to leave all 
the internal corners a little rounded. 

It may be useful, perhaps, to add that cutters 
which are required for cutting soft substances, such 
as brass or copper, require to have their teeth very 
sharp, and to be made very hard. The teeth require 
also to be cut much coarser than for iron or steel, 
otherwise they soon become choked with the metal, 
and become hot, and very soon lose their sharp edges, 
and will not cut, as the term is, sweet, but would pol- 
ish and glide over the metal almost without effect, 
were the cutters not seconded by a great amount of 
power. 

"When a steel tool or piece of work similar in 
shape to a piece of a bar of round steel, say, two, 
three, four, or more inches in diameter, and three, 
four, five, or more inches in length is required to be 
hardened, it frequently becomes necessary, previous 
to hardening such a tool or piece of work, to bore a 
hole through the centre of it, in the direction of its 
length, in order that the water may pass through 
the hole, and cool the steel more equally, and reduce 
the risk of its breaking. But as the two ends are 
even then always likely to become cool 'first, it 
would not be amiss to widen the hole a little more 
in the centre than at the ends, and so further reduce 
the risk of its breaking in hardening. 



HARDENING- AND TEMPERING OF STEEL. 87 

•It is unnecessary, perhaps, to remark, that the 
largest size screw-taps and hobs are very liable to 
break in hardening, and, though a hole might be 
bored through them to prevent their breaking, still 
this would not give a very pleasing appearance, nor 
would it look very mechanical. Independent of the 
appearance of the tap or hob, a hole through large 
screw-taps or hobs would be very apt to cause them 
to become oval in hardening • and if this did occur 
it would cause the tap, when in use, to make the hole . 
larger than it was intended to do, and cause the hob 
when in use to cut very unequally and very slowly, 
because only two opposite sides of the hob could be 
made to cut. 

It is obvious that a round piece of steel having a 
plain or smooth surface, and which has a hole bored 
through it in the direction of its length, would be as 
likely to become oval in hardening as a piece of 
steel having a similar hole through it and a screw 
upon its surface, such as a tap or hob. But then 
there are means by which a plain surface can be 
made true again after hardening, such as by lap- 
ping or grinding, whereas with taps or hobs these 
methods cannot be adopted. In all cases it must 
be borne in mind that, the more uniformly articles 
are heated, the less liable are they to become crooked 
or oval in hardening. 

For the various reasons above given, another 
method differing from the boring of holes through 
large taps or hobs may be adopted, a method which 
will not at all disfigure the taps or hobs, or cause 
them to become oval, but which will cause them to 



88 HARDENING AND TEMPERING OF STEEL. 

harden and cool more uniformly, at the same time 
prevent them breaking. It is this : to turn the 
plain part of the tap or hob as small as it will con- 
veniently bear without encroaching upon the re- 
quired strength of the tap or hob, and to cut the 
concave grooves (which are in the direction of the 
length of the best kinds of taps) a little deeper than 
what they are generally cut. 

The method of reducing the steel in that part of 
large articles which is the last to become cold when 
they are immersed in the water, cannot with some 
kinds of articles be adopted ; because, were the steel 
to be reduced in that particular part, it would unlit 
the articles for the purpose for which they are in- 
tended. This would be the case with large circular 
dies, which frequently require to be turned flat on 
both sides. It is obvious that the method of boring 
holes through these kinds of articles, or turning the 
sides of them concave, cannot be adopted ; con- 
sequently another method must be resorted to. It 
is this : to heat an iron ring or collar, and while the 
die is in a cold state shrink the heated ring tight 
upon the die ; this method will, when the die is 
heated and immersed in the water, lessen the risk 
of fracture. 

It will be imagined, perhaps, that the object of 
shrinking a ring upon the die is to compress the 
die, and by compressing the die it will keep it from 
breaking ; now, if this were the object, it would be 
a step in the wrong direction. The object of shrink- 
ing a ring upon the die is to prevent the water from 
cooling the outside of the die too suddenly. It 



'hardening and tempering of steel. 89 

must be borne in mind that the more suddenly the 
heat is extracted from the steel, the more sudden is 
the contraction of the surface steel ; and the more 
sudden the contraction of the surface steel, the more 
sudden and greater is the compression of the in- 
terior steel ; and the more sudden and greater the 
compression of the interior steel, the greater is the 
risk of the steel breaking by the outer crust being 
held for the moment in a greater state of tension 
(strain). The more the interior steel is compressed 
the more dense it becomes ; consequently, when it 
becomes cold it occupies less space than what it oc- 
cupied previous to hardening, and the result is an 
internal fracture. 

It will not be out of place, perhaps, to remark, 
that if every mechanic were made more acquainted 
with the chemical properties of the material, and the 
action of fire and water upon the material, thousands 
©f articles which have been thrown aside might have 
been prevented from being burnt in forging, and thou- 
sands more would have been saved from being cracked 
in hardening ; and the price paid upon the forging, 
annealing, turning, fitting, and hardening, or making 
articles from bad material, might have been saved. 

Suppose a similar block of steel to the one just 
treated of to be required for a large friction-wheel, 
the method of shrinking a ring upon it previous to 
hardening of it will not answer, because the ring 
would prevent the water from effectually hardening 
the steel in that part which is required the hardest ; 
consequently the same methods will have to be 
adopted with this kind of article as those which are 



90 HARDENING AND TEMPERING OF 8TEEL. 

to be adopted with a large circular cutter, either 
boring holes through it or turning the sides concave. 
Suppose an eccentric steel collar is required to be 
hardened, for example. Let us suppose the hole in 
the collar where the shaft or mandrel passes through 
to be about two inches in diameter, and the thick- 
ness of the metal one inch and a half on one side 
and about the quarter of an inch on the opposite 
side, from the irregular form of this article it will 
easily be seen that there is great risk of its breaking 
in hardening. The unequal thickness of the steel 
causes unequal contraction, one side of the collar 
being so £hin it is cool almost instantly. The stout 
side contracts after the thin side is fixed, the thin 
side in its then hard state cannot give, consequently 
it breaks. Before such an article as this is sent to 
the hardener, a pifice of iron should be fitted to the 
thin side of it so as to make both sides about equal 
in thickness. The iron must be fitted to the inside, 
as it is the outside of the collar which is required 
hard. This piece of iron is to prevent the thin part 
of the collar from cooling too suddenly, and thus 
prevent the collar breaking. The piece of iron, of 
course, must be bound upon the collar with a piece 
of binding wire, after which it is ready for harden- 
ing. I may here remark, that a square lump of 
steel is less liable to break in hardening than either 
a cylindrical or spherical lump, even though there be 
more bulk in the square lump than what would 
form either the spherical or the cylindrical lump. 

Although this is such an important subject, and 
much- more might be said, still it is not necessary, 



HAKDEKTNG AND TEMPERING OF STEEL. 91 

perhaps, to enlarge more upon it, as the mind will 
have discovered by this time, the method of proceed- 
ing with tools or articles of any description requir- 
ing a great amount of labor and time to make them ; 
and where there is great clanger of their breaking 
in hardening. The same or similar methods will 
have to be adopted in all cases where large masses 
of steel require to be hardened, if we wish to obtain 
satisfactory results. 

The information here afforded, coupled with 
the workman's own experience and ingenuity, will, 
doubtless, be sufficient to prevent his finding diffi- 
culty in forming for himself any particular idea upon 
the subject he may want ; consequently I will now 
pass on to the process of hardening and tempering. 

In the process of hardening steel, water is by 
no means essential, as the sole object is to extract 
its heat rapidly ; and the more sudden the heat is 
extracted, the harder the steel will be ; consequent- 
ly, those substances which act most suddenly upon 
the steel will produce the greatest effect, though 
they will not always produce the most satisfactory 
results, for intense cold has a very unfavorable 
effect upon steel. Good cast steel receives by sud- 
den cooling a degree of hardness almost equal to 
that of the diamond, and almost sufficient to cut, 
or make an impression, upon every other substance; 
and, when of the best quality, and the hardness not 
carried to extreme, a certain amount of tenacity is 
also combined with the hardness. 

If steel is heated to a red heat, and allowed to 
cool gradually, it becomes nearly as soft as pure 



92 HARDENING AND TEMPERING OF STEEL. 

iron, and may, nearly with the same facility, be 
worked into any required form. If steel be too 
hard, it will not be proper for tools, or instruments 
of any description, which are required to have very 
keen edges, or very fine points, because it will be 
so brittle that the edges will soon become notched, 
or the points break off on the slightest application 
to the work ; if, on the contrary, the steel be too 
soft, the edges or points will turn or bend ; but, if 
the steel is duly tempered, it will resist breaking 
on the one hand and bending on the other. 

The degree of heat required to harden steel is 
different in the different kinds. The best kinds 
require only a low red heat ; the lowest heat neces- 
sary to effect the desired purpose is the most ad- 
vantageous, and to impart to it any extra portion 
of heat must partly destroy its most valuable prop- 
erties ; and for this misfortune there is no remedy, 
for, if cast steel is overheated, it becomes brittle, 
and can never be restored to its original quality ; 
therefore, it will be quite incapable of sustaining a 
cutting edge, but will chip or crumble away when 
applied to the work. 

There are various ways of applying the heat to 
articles when they require to be hardened. The 
methods to be adopted will of course depend upon 
the shape and size of the articles ; also, upon the 
quantity requiring to be operated upon, for in some 
instances a large quantity can be heated and hard- 
ened as expeditiously as a single article. Some- 
times it is requisite to heat the articles in the* midst 
of the fuel in a hollow fire ; sometimes it is requi- 



HARDENING AND TEMPERING OF STEEL. 93 

site to heat them in an open fire ; and sometimes 
it is requisite to enclose and surround them with 
carbon in a sheet-iron case, or box, and heat the 
whole in a hollow fire, or in a suitable furnace ; at 
other times, or in some instances, it is more conve- 
nient to heat them in red-hot lead. When a laro-e 
quantity of some kinds of articles is required to be 
hardened, the method of heating them in red-hot 
lead is very convenient and very economical ; but to 
be constantly employed dipping articles in red-hot 
lead is, I believe, very injurious to health. I have 
myself been so employed, and have felt its very bad 
effects ; and I have, therefore, avoided using it as a 
source of heat, except in cases, of great necessity. 

A more uniform degree of heat can be snven to 
some articles by heating them in red-hot lead, than 
by any other means, especially some kinds, which 
are of great length ; consequently, they will keep 
their proper shape better in hardening. A gas- 
flame, or the flame of a candle, is very convenient 
for heating the point of some small articles ; some 
small articles may be sufficiently heated by placing 
them between the red-hot jaws of a pair of tongs. 
Some small articles may be heated by taking a 
piece of bar-iron, and, after heating it to redness, 
cutting it half way through with the chisel, and 
then placing the articles in the nick, which will 
heat them sufficient for hardening. Sometimes it is 
necessary to insert a piece of iron pipe in the midst 
of the ignited fuel of the fire, and then to place the 
articles in the pipe. 

When a large number of steel articles are 



94: HARDENING AND TEMPERING OF STEEL. 

required to be hardened all over, or throughout 
their body, and which are too small to be heated in 
the midst of the ignited fuel of a hollow or open 
fire, and perhaps it is inconvenient to heat them in 
red-hot lead, or if it be thought hazardous to enclose 
them entirely in a sheet-iron box, from an appre- 
hension that the heat might increase too much, the 
following scheme may be adopted. Place as many 
of the articles at once as may be convenient to 
manage into a sheet-iron pan, without a lid, and 
cover them with charcoal dust, place the whole in 
a furnace or hollow fire, and slowly heat them to 
redness. They should be occasionally, and carefully 
moved about in the pan by the use of a small wood 
or iron rod, in order to equalize the- heat ; the char- 
coal dust prevents the articles from scaling so read- 
ily, and has a tendency to prevent the rod bending 
them when moving them about in the pan. When 
the articles arrive at the proper heat they may be 
immersed in water or oil, or water with a film of 
oil upon the surface, according to the degree of 
hardness required in them. 

A rod of good steel in its hardest state is broken 
almost as easily as a rod of glass of the same dimen- 
sions, and this brittleness can only be diminished 
by diminishing its hardness; and in this manage- 
ment consists the art of tempering. The surface 
of the hardened steel is brightened, and it is exposed 
to heat. As the heat increases there is a curious 
and uniform change in the clear color of the sur- 
face. The colors which appear upon the surface 
of the steel are supposed to be the result of oxida- 



HARDENING AND TEMPERING OF STEEL. 95 

tion. The thickness of the coat or film of oxide, if 
such it be, determines the color, and the thickness 
of the coat depends upon the temperature to which 
the work is exposed. 

It is quite probable that these colors are the 
result of oxidation ; but the present state of my 
knowledge does not enable me to prove that these 
colors would not appear if the steel could be heated 
in a vacuum, a space unoccupied with air, neither 
does the present state of my knowledge enable me 
to prove that these colors are not due to the new 
arrangement of the particles, quite independent of 
any chemical change ; but, let the cause be what 
it may, these colors are a very useful index, for by 
them any degree of hardness retained by the steel 
may be ascertained. The colors which successively 
appear on the surface of the steel, slowly heated, 
are a yellowish white or light straw color, a dark 
straw, gold color, brown, purple, violet, and deep 
blue. Finally, the steel becomes red hot, and a 
black oxide is formed. It will be more readily 
imagined that the various colors are the result of 
oxidation, when it is seen that the action of the 
oxygen of the atmosphere upon the steel in a red- 
hot state converts the surface of the steel into a 
black oxide ; and this black oxide, like the various 
colors, increases in thickness with increase of tem- 
perature, and if it is hammered or scraped off it is 
again quickly formed. 

There are various ways of applying the heat for 
tempering or reducing the hardness in steel articles. 
The methods to be adopted will, of course, depend 



96 HARDENING AND TEMPERING OF STEEL. 

upon the shape and size of the articles ; also upon 
the quantity requiring to be operated upon ; for in 
some instances a large quantity can be tempered as 
expeditiously as a single article. The heat for tem- 
pering should not be too suddenly applied, as a cer- 
tain amount of time is essential for the particles to 
rearrange themselves, and the slower the heat is 
applied the tougher and stronger the steel becomes. 
When it is required to temper an article or articles 
to any of the colors previously spoken of, they must 
be brightened after they are hardened. But before 
proceeding farther it will perhaps be well to state 
that previous to brightening the articles the hard- 
ener ought always to make himself sure that the 
articles are quite hard. If the articles are not prop- 
erly hardened, or, in other words, if the articles- are 
not possessed of a certain degree of hardness, it will 
be time and labor lost afterward to temper them ; 
besides, the articles will be practically useless for 
the purpose they are intended for until they have 
been hardened and tempered over again. There- 
fore, in order to make sure of good work, the hard- 
ener should always try the hardness of the steel 
with a smooth file, a file finely cut. It has already 
been inquired of me, and may be inquired again, 
perhaps, why is it necessary for a practical man 
who is thoroughly acquainted with the quality of 
the material he is hardening, likewise with the 
temperature suitable to harden the material, to try 
the hardness of the steel, when he knows from ex- 
perience that the steel hardens properly at a certain 
temperature? The answer to this is, the hardener 



•HARDENING AND TEMPERING OF STEEL. 97 

may be a practical man, and may be thoroughly 
acquainted with the quality of the material, like- 
wise with the temperature suitable to harden the 
material ; but if he is not a careful man his knowl- 
edge will be of little service, an,d the necessity for 
trying the hardness of the steel before it is tempered 
is soon made evident : besides, if proper attention 
is not paid to the water it will deceive the hardener. 
Again, the most careful and experienced hardener 
is liable to be deceived in the temperature of the 
steel when hardening in twilight. It has previously 
been stated, that it is requisite at times to enclose 
some kinds of articles, when they require to be 
hardened, in a sheet-iron box, and surround them" 
with charcoal. When this method is adopted, the 
articles will require a much more considerable 
amount of time to heat them than is readily ima- 
gined by those who are not accustomed to this 
method. Charcoal is a bad conductor of heat, and 
if the hardener be unacquainted with the conduct- 
ing quality of the charcoal, he will be apt to draw 
the box out of the fire and immerse the contents in 
the water, before the central articles have acquired 
the proper temperature suitable for hardening them, 
and those- articles which are below a certain heat 
cannot become hard. Here again is exhibited the 
necessity of trying whether all the articles are hard 
before beginning to temper them. In some instan- 
ces (though the steel be the very best that Sheffield 
can furnish), one or two badly tempered articles 
would get the manufacturer of them a bad name, 
and would in some instances get all the order con- 



98 HARDENING AND TEMPERING OF STEEL. 

derailed, even if all the other articles were right. 
The use of the file for proving whether the articles 
are hard can be dispensed with when the articles 
are brightened on an emery-wheel, or a small dry 
grinding-stone running at a quick speed, for the 
person employed to brighten them will find, if they 
are properly hardened, plenty of brisk, lively sparks 
fly from them when they are held upon the emery- 
wheel or the grinding-stone. But if they are not 
hard there will be very little fire in them. There- 
fore, with a very little attention, these articles which 
are soft (if any there be) can be detected, and may 
be put aside and heated again with the next batch. 

After the articles are brightened, the hardness 
can be reduced to any particular standard, by pla- 
cing them upon a hot bar or plate of iron, or upon 
the surface of melted lead, or in a bath of a more 
fusible metal kept at a certain heat, or in hot sand, 
or burning charcoal, or the articles may be held in 
the inside of an iron ring heated to redness, or they 
may be placed in the mouth of a furnace, or in an 
oven heated to the proper temperature, or they may 
be placed in or upon a gas-stove specially con- 
structed, or they may be heated in any other con- 
venient way. 

The above methods of applying the heat for 
tempering are to suit those kinds of articles which 
have been wholly quenched. When any of the 
above methods of applying the heat is adopted, and 
the articles are exposed to a higher degree of heat 
than that which is required to reduce them to the 
exact temper, they must be removed from the heat 



HARDENING AND TEMPERING OF STEEL. 99 

immediately they attain the desired color, other- 
wise the temper will become too far reduced, or in 
other words the articles will be too soft for the pur- 
pose they are intended for. After they are removed 
from the heat they may be immersed in water or 
oil, or they may be allowed to cool in the air of 
their own accord ; for it matters not which way 
they become cold, providing the heat has not been 
too suddenly applied ; for when the articles are re- 
moved from the heat they cannot become more 
heated, consequently the temper cannot become 
more reduced. But those kinds of tools which are 
heated further than what they are required hard, 
such as a large portion of the small kinds of turning- 
tools, cold chisels, and the larger kinds of drills, and 
numbers of other kinds of tools, and which are only 
partially dipped, and which are afterward tem- 
pered by the heat from the back of the tool, must 
be cooled in the water the moment the cutting part 
attains the desired color, otherwise the body of the 
tool will continue to supply heat, and the cutting 
part will become too soft. 

It is, perhaps, too obvious to require remark, 
unless it be for the information of those who are un- 
accustomed to these processes, that if, after temper- 
ing an article it proves too hard for the purpose it 
is intended for, it is not absolutely necessary to 
reharden it, though in some instances it is more con- 
venient to do so, the temper may be farther reduced 
by exposing it again to heat ; but, if an article is 
too far reduced in temper, it becomes then absolute- 
ly necessary to harden it over again. When a very 



100 HARDENING AND TEMPERING OF STEEL. 

large number of small articles are required to be 
tempered, it will be too slow a process to temper 
them to a certain color; therefore, a more expedi- 
tious method must be adopted. A very convenient 
way of tempering a large quantity of small articles 
at once, and of heating them uniformly, no matter 
how irregular their shape, providing the heat is not 
too suddenly applied, is to put them into a suitable 
iron or copper vessel with as much tallow or cold 
oil as will just cover them, and then to place the 
whole over a small lire and slowly heat the oil un- 
til a sufficient heat is given to the articles for the 
temper required. It may be well, perhaps, to re- 
mind the young mechanic that the temperature of 
the oil or tallow may be raised to six hundred de- 
grees of heat, or rather more ; consequently, anj; 
temperature below a red heat may be given to the 
articles by the heated oil. Certain degrees of tem- 
per retained by steel articles when they are heated 
in oil may be estimated by the following circum- 
stances : when the oil or tallow is first observed to 
smoke, it indicates the same temper as that called 
a straw color. The temperature of the oil, if meas- 
ured by the thermometer, will be about 450 de- 
grees. 

If the heat be continued, the smoke becomes 
more abundant, and of a darker color; this indi- 
cates a temper equal to a brown. The tempera- 
ture of the oil at this stage, if measured by the ther- 
mometer, will be about 500 degrees. If the oil or 
tallow be heated so as to yield a black smoke and 
still more abundant, this will denote a purple tern- 



• HARDENING AND TEMPERING OF STEEL. 101 

per. The temperature of the oil at this stage, if 
measured by the thermometer, will be about 530 de- 
grees. The next degree of heat may be known by 
the oil or tallow taking fire if a piece of lighted 
paper be presented to it, but yet not so hot as to 
burn when the lighted paper is withdrawn. This 
will denote a blue temper. The temperature of the 
oil at this stage, if measured by the thermometer, 
will be about 580 degrees. If the articles are lifted 
out of the vessel at this period, they will be found 
to possess a considerable amount of elasticity. This 
temper is not unfit for some kinds of springs, but 
only when a rather mild kind of steel is employed ; 
the steel in this state may be wrought, that is, it 
may be turned or filed, though with difficulty. 

The next degree of heat may be known by the oil 
or tallow taking fire and continuing to burn, at the 
same time rising higher in the vessel. If the arti- 
cles are lifted out of the vessel at this period, the 
oil will burn upon them with a white flame. This 
is the temper which is mostly used for spiral and 
some other kinds of springs. 

If the whole of the oil or tallow be allowed to 
burn away before the articles are lifted out of the 
vessel, it imparts the temper which clock-makers 
mostly use for their work. This temper is the low- 
est used, when the steel is required to be at all harder 
than in its natural state ; for a small degree of heat 
more would just be seen (red) in a dark place. 

Any single article, to spare the trouble of heat- 
ing it in a vessel with oil or tallow, may be smeared 
with oil or tallow and held over a clear fire, or over 



102 HARDENING AND TEMPERING OF STEEL. 

a piece of hot iron ; or, if the article is small, it may 
be held in a gas -flame, or in the flame of a candle, 
and its temper, when heated, ascertained in a similar 
manner. It will not, perhaps, be out of place to 
state, that I was once asked by a young man the 
way to harden and temper spiral springs made of 
steel wire. I informed him that he must first of all 
harden them either in water or oil, according to the 
substance of the steel ; and, if he had a sufficient 
quantity to do which would pay for the waste of the 
oil, it would be a very convenient and expeditious 
method to tie them all together with a piece of 
iron wire, and place them in an iron saucepan or 
any other suitable vessel he might chance to have, 
with as much oil or tallow as would cover them, 
and then to place the whole over a small fire, 
and slowly continue the heat until the oil takes fire, 
and continues to burn ; after which, to lift the 
springs out of the vessel by means of an iron rod, 
and then to give them one dip into some cold oil. 
This, was to give the springs a black color ; they 
were then to be allowed to cool in the air of their 
own accord. 

When I gave the above information, I did not 
think for one moment that this young man would 
attempt to boil the oil over the fire in the dwelling- 
house ; but he informed me that he did so, and the 
result was that he nearly set the house on fire. I 
have just mentioned this circumstance merely as a 
warning to those who are unacquainted with the 
nature of oil at this high temperature, so that they 
may not fall into the same error; they must not 



HARDENING AND TEMPERING OF STEEL. 103 

attempt to* boil oil unless they have a place suitable 
for it, or serious accidents may happen. 

Before putting any article in the fire to heat it 
for hardening, it is necessary to examine its shape 
in order to know which way it will require to be 
immersed in the water so as to lessen the risk of its 
cracking ; every kind of article requires to be dipped 
a particular way according to its shape. For in- 
stance, if the article is unequally thick and thin, or in 
other words, if there is a stout part and a thin part, 
the stoutest part should always enter the water fore- 
most. By dipping the article with the stoutest part 
of it entering the water foremost, it causes the steel 
to cool more uniformly, and lessens the risk of frac- 
ture. If the thinnest part of the article be allowed 
to enter the water foremost, it increases the risk of 
fracture, because it will become cool much sooner 
than the stouter paft of the article, consequently 
the stout part of the article contracts by the loss of 
heat after the thin part is fixed ; the thin part in its 
then hard and brittle state cannot give, consequent- 
ly it breaks ; or, if it does not break at the time of 
the hardening of it, it is held in such a state of 
tension (strain) that it is ready to break when ap- 
plied to the work. 

Though it is requisite when hardening steel 
articles to let the stoutest part of the articles enter 
the water foremost, in order to allow the steel to 
become cool more uniformly, still it is not practi- 
cable in all instances to get the stoutest part of the 
articles into the water foremost, as will subsequent- 
ly be shown. 



104 HARDENING AND TEMPERING OF STEEL. 

9 

"When it is not practicable to get the stoutest 
part of some kinds of articles into the water fore- 
most, some other method which will keep the thin 
part of the articles from cooling too suddenly, and 
which will cause the steel to become more uniform- 
ly cool, must be resorted to. The various methods 
to be adopted for lessening the risk of fracture 
when hardening various kinds of articles, will be 
explained as we go along. 

The water which is to be used for hardening 
steel tools, or any other kind of articles made of 
steel, should neyer be quite cold, but should have, 
as the term is, the chill taken off; or, to use other 
words, the water requires to be made a few degrees 
warmer. The reason for this is, that when water, 
of too cold a temperature is used, it abstracts the 
heat so suddenly from the surface of the steel, that 
it causes a too sudden contraction of the surface 
steel, and the expansion of the interior steel in its 
still red-hot state is more than the hardened crust 
can bear, consequently it frequently causes the steel 
to break. 

It is quite probable that the interior steel for 
the moment becomes both heated and expanded in 
a higher degree by the sudden compression, for the 
sudden contraction of the surface steel by the sud- 
den loss of heat must act on the interior steel some- 
thing similar to a blow from a heavy hammer or 
the pressure of a squeezer ; and if the steel should 
happen to be a little too hot at the time of dipping 
it into pure cold water, there is as much danger of 
its breaking as there is of a glass bottle breaking 



• HAEDEJsrusra and tempering of steel. 105 

when boiling water is poured into it ; lieat and 
cold act on glass and other brittle substances in a 
similar manner that they act on steel. When boil- 
ing water is poured into a glass bottle, the expan- 
sion of the inside glass is so sudden that it is more 
than the outside can bear, consequently the bottle 
breaks ; if the glass is heated to a red heat and 
plunged into cold water, it breaks into a quantity 
of small pieces from the sudden contraction ; if a 
stone is thrown into the fire, it breaks from the sud- 
den expansion of its surface. 

The more the water is used for hardening steel 
the softer it becomes, and has a tendency to act less 
suddenly upon the steel ; consequently the less fre- 
quently the water used for the purpose is changed 
the better it is for hardening the steel — that is, pro- 
viding the water has not by continual use become 
greasy. The water is not made better for giving 
the steel a greater degree of hardness by being long 
in use, but it is made better for the purpose because 
it is less likelv to crack the steel than fresh water : 
therefore, as the water wastes, fresh water should 
be added to it. As it is necessary to clean the 
tank out occasionally, it would be well before using 
fresh water to make it quite hot, by putting bars 
of hot iron into it and allowing it to become nearly 
cold again before using it, or the chill may be 
taken off the water and the water made softer by 
putting some ignited charcoal or wood-ashes into 
it. It is obvious that the colder the water the 
more effectually it hardens the steel, and the more 

especially when the steel is immersed suddenly 
5 



10G HARDENING AND TEMPERING OF STEEL. 

and a rapid movement given to it whilst it is be- 
coming cool ; but when fresh cold water is used 
there is always greater danger of the steel cracking. 
Brinish liquids, such as aquafortis, urine, or water 
charged with common salt, etc., produce rather 
more hardness than plain water ; but, for most arti- 
cles, plain water with the chill off gives sufficient 
hardness to the steel. Water at about sixty degrees 
measured by the thermometer is the most suitable 
temperature to prevent steel cracking in hardening. 
Water holding soap in solution prevents the steel 
from hardening. There are certainly some kinds 
of. tools, also some pieces of work used in machin- 
ery, which require to have a greater amount of 
hardness given to them than can be given by plain 
water ; there are some kinds of gauges, burnishers, 
and certain kinds of dies which require to be very 
hard, so that it becomes necessary at times to use a 
saline liquid ; a file requires also to have a nice 
hard tooth. When steel is required to be made ex- 
tremely hard it may be quenched in mercury, the 
chemists' name for quicksilver ; but this fluid it is 
obvious can onfy be used on a small scale. 

All bright articles which are made of steel and 
which require to be hardened are the better for 
being heated, previous to immersion, in contact 
with carbon. By heating steel in contact with car- 
bon, or by supplying a small quantity of carbon to 
the surface of the steel after it is heated, it favors 
the steel in hardening ; but, though it is better to 
supply a small quantity of carbon to the surface 
of the steel, still it is not absolutely necessary to do 



'HARDENING AND TEMPERING OF STEEL. 107 

so, because very satisfactory results are obtained 
with some kinds of articles by heating them in red- 
hot lead previous to immersion. "When red-hot 
lead is used as a source of heat, the method of sup- 
plying carbon to the surface of the steel cannot 
conveniently be adopted ; neither can the method of 
supplying carbon to the surface of the steel be con- 
veniently adopted when some other methods of 
heating steel are adopted, such as heating some 
small steel articles between the heated jaws of a pair 
of tongs, or between two heated pieces of bar iron, or 
in a gas-flame, the flame of a candle, etc. To sup- 
ply carbon to the surface of steel articles, the arti- 
cles may be enclosed in a sheet-iron case or box, 
and surrounded on all sides with either wood char- 
coal or animal charcoal ; the whole will require to 
be placed in a furnace or hollow fire and heated to 
redness. Wood charcoal is too familiar to every 
one to require remark in this place ; but it may be 
necessary to state that the animal charcoal here 
spoken of is nothing more than any animal matter 
— such as horns, hoofs, skins, or leather, etc., just 
sufficiently burnt to admit of being reduced to 
powder. If it is found more convenient to heat 
the articles in the midst of the ignited fuel of an 
open or hollow fire, it is advisable to do so ; but 
when any bright steel article is heated in an open 
or hollow fire, free of wood or animal charcoal, it 
ought always to be coated with prussiate of potash, 
or some other substance which will, after it has ar- 
rived at a red heat, protect it from the direct action 
of the lire and water, at the same time supplying 



10S HARDENING AND TEMPERING OF STEEL. 

a small portion of carbon to the surface of the steel. 
Though bright steel when heated in the midst of 
the ignited fuel of a hollow or open fire is the better 
for being coated with the prussiate of potash, still 
their are instances when it will be advisable not to 
use it; for instance, if the potash were used in 
hardening saws which require to be sharpened with 
the file it would cause greater difficulty to file them, 
consequently, in such an instance, the potash should 
not be used. When it is required to coat any steel 
article with the prussiate of potash, the article will 
require to be heated to redness before the potash is 
put on to it, otherwise it is useless to put it on, for 
the steel requires to be sufficiently hot to fuse the 
potash when first it is applied for the potash to be 
of any practical service to it. The potash should 
always be finely powdered and placed in a small 
box, the lid of which should be full of small holes, 
similar to a grater or pepper-box. The reason for 
this is that it is the most economical way of using 
it, especially if the article is held over a piece of 
plate iron whilst the potash is being put on ; what 
portion of the potash falls upon the plate must be 
returned to the box, and thus prevent it being 
wasted. 

After heating any steel article to redness and 
sprinkling the potash upon it, it must be returned 
to the fire for a few minutes, or until it attains the 
desired heat; the article is then ready to be im- 
mersed in the water. Sometimes when the article 
is very large it is necessary to draw it from the fire 
a second time and sprinkle it again with the potash, 



' HARDENING AND TEMPERING OF STEEL. 109 

in order to s;ive it a thicker coat before it is im- 
mersed in the water. 

Steel which is hardened with the skin upon it, 
will undoubtedly be the better if it be sprinkled 
with the prussiate of potash ; for it has always a 
tendency to penetrate through the thin oxide, and 
supply carbon to the surface of the steel, which, 
perhaps, there is no necessity for repeating, is favor- 
able to the steel in hardening. 

It may be well to state that the access of air to 
the potash should always be prevented, when the 
potash is not in use. 

Steel in the state it leaves the forge, with the 
skin or thin scale upon it, is less liable to break in 
hardening than steel which is brightened previous 
to hardening. The skin or thin scale upon the 
steel prevents the water from acting too suddenly 
upon the steel ; consequently the contraction is 
slower. Common turning-tools will always stand 
better ; that is, they will keep a finer and firmer 
edge, if they are hardened with the skin upon them, 
than they will if they were brightened (either by 
filing or grinding) previous to hardening ; in fact, 
all tools that can be ground and sharpened upon 
the grinding-stone after they are hardened, will be 
the better for being hardened with the skin upon 
the steel ; and, if properly forged by the tool-smith 
(who is generally as well acquainted with the prop- 
er shape of tools, as the mechanic who uses them), 
the tools will require very little grinding ; and, as 
for water-cracks in the steel, there will be none. 
When turning-tools are made of the best cast steel, 



110 HARDENING AND TEMPERING OF STEEL. 

and hardened previous to the removal of the skin 
or scale, and which are not intended to have very 
keen edges, but which are intended to sustain a 
good hard edge for cutting iron and other metals 
(cast iron especially), they will not require to be 
tempered after being made hard, but the heat 
should be carefully regulated at first, as the most 
useful hardness is produced by that degree of heat 
which is just sufficient to effect the purpose ; for it 
is quite reasonable to suppose that the hardness of 
steel depends upon the crystallization, and the in- 
timate combination of its carbon ; therefore, the 
heat which effects this must be the best. 

As there are a number of tools used in the 
turnery which cannot be ground upon the grin ding- 
stone, owing to their peculiar shapes, it becomes 
necessary then, whilst the steel is in its soft state, 
to fit these kinds of tools up with the file, or to form 
them in the lathe, or some other machine ; con- 
sequently these kinds of tools cannot be hardened 
with the skin upon them. But, as there is greater 
liability of brightened steel breaking in hardening 
than that which is not brightened, and as some 
kinds of tools cannot be ground after they are hard- 
ened, it becomes an object of importance that they 
should stand well. Therefore, extra precautions 
must be used when hardening these kinds of tools ; 
for, were their cutting-edges to chip through being 
a little too hard, or rub off through being a little 
too soft, they will be practically useless for the pur- 
pose they are intended for, until they have been 
softened and fitted »up again, and subsequently 



HARDENING AND TEMPERING OF STEEL. Ill 

hardened. In some instances the tools would be 
wholly useless ; this would be the case with screw- 
taps, and some kinds of rimers, broaches, etc., for 
their original sizes would be lost. It must be ob- 
vious, then, that if extra care is required with some 
kinds of tools, it must be with those kinds which 
take a great amount of labor and time to make 
them, also with those kinds which cannot be re- 
paired. 

It is well known that, when iron is heated to a 
high temperature, and forged upon the anvil, a 
thick unequal scale is formed upon the surface of 
the iron, by the action of the oxygen of the atmos- 
phere ; and if steel is heated to the same degree, 
and forged upon the anvil, a thick unequal scale is 
formed upon its surface in a similar manner as it is 
formed upon the surface of iron. This thick un- 
equal scale would cause the steel to harden un- 
equally, if it were not removed previous to hard- 
ening of the steel ; but it must be borne in mind, 
that, when tools are made of the best cast steel, and 
forged at the proper heat, and the anvil kept clean 
during the time they are being forged, it will pre- 
vent this thick unequal scale being formed ; but a 
very thin equal skin or scale will be formed. This 
thin equal scale does not prevent the steel from 
hardening equally, neither does it prevent the steel 
becoming sufficiently hard for most purposes ; but 
it will prevent the surface steel becoming cool 
too suddenly, consequently it must be obvious that 
it will have a tendency to prevent the steel break- 
ing in hardening. 



112 HARDENING AND TEMPERING OF STEEL. 

When steel is required to possess the greatest 
possible degree of hardness, it is obvious that the 
scale must be removed previous to hardening of it. 

There are many large steel articles broken after 
hardening them, by taking them out of the water 
before they are thoroughly cold ; and, perhaps, a 
few words upon this will not be out of place. It is 
the opinion of many mechanics that the cause of 
steel breaking after it is lifted out of the water is 
the action of the air upon the steel, when first the 
steel comes in contact with the air. It is true that 
large masses of steel frequently break immediately 
the steel is lifted out of the water ; but I am at a 
loss to see in the slightest degree what effect the 
air can have upon the steel in this instance. My 
opinion is this, and which I have formed from ex- 
perience, that if the steel does not break during the 
time it is becoming cool, there is no more danger of 
its breaking after it is lifted out of the water than 
what there was of its breaking in the water, that is, 
providing the steel be allowed to remain in the 
water until its centre becomes quite cool. During 
the time the steel is in the water becoming cool, 
and after a certain amount of heat is abstracted 
from the outer crust, there is a peculiar motion or 
vibration of the interior particles in rearranging 
themselves according to their form. This peculiar 
motion weakens the cohesion of the particles. The 
tension of the steel at this period is in one direction ; 
but let the steel be lifted out of the water before 
the central steel has become quite cool, and the 
tension is reversed in an opposite direction. This 



■HARDENING AND TEMPERING OF STEEL. 113 

is caused by the central steel imparting heat to the 
inner side of the hardened crust ; and this sudden 
change is frequently more than the hardened crust 
can bear, and causes the steel to break. If the steel 
does not break, it is held in such an unequal state 
of tension, from the particles not being allowed suf- 
ficient time before they were again disturbed to 
assume the exact arrangement to which they are 
naturally disposed, that the tenacity of the steel 
must more or less be weakened. It is not requisite 
that the steel should lie in the hardening tank until 
the steel and the water become quite cool ; for in 
some instances the steel article is required for im- 
mediate use. In such instances, any vessel, such as 
a hand-bowl or a water-bucket, etc., may be sunk 
into the tank, and the steel article or articles may, 
while the vessel is under the surface of the water, 
be lifted into the vessel ; after which the vessel can 
be lifted out, with as much water in it as will cover 
the article or articles. The vessel may then be 
sunk, with the article or articles still in it, into 
another tank of quite cold water, or the vessel may 
be placed under a water-tap, and cold water run 
upon the articles ; and when they are quite cool 
they can be lifted out with safety. It will be ob- 
vious that the greater the mass of steel the greater 
the risk of its breaking by being removed from the 
water before it is thoroughly cold. 

There are many articles cracked in hardening 
by heating them all over, or throughout their body, 
and then partially dipping them into the water. 
All kinds of articles which are heated all over are 



114: HARDENING AND TEMPERING OF STEEL. 

the better for being dipped and hardened all over ; 
and then, if one part of the article is required softer 
than the other parts, it is best to soften it after. 
To spare this trouble, at the same time lessen the 
risk of fracture, it will be well not to heat some 
kinds of articles in any other part but that which 
is required hard, and then to entirely quench them. 
The heat of course must not terminate upon the 
article in a strict line, but should be gradually 
tapered off. It is obvious that the heat will not 
terminate in a strict line when the article is heated 
in a common smith's fire ; but, when red-hot lead 
is used as a source of heat, the heat upon the article 
is liable to terminate in a strict line unless a vertical 
movement be given to the article. If only a cer- 
tain part of a steel article is required to be hard- 
ened, and the article be heated throughout its body, 
and the water into which the article is to be put be 
quite cold, and the hardener in dipping it stop at any 
particular part, at the same time holding it quietly 
without giving it a movement whilst it is becoming 
cold, there is always great danger of the article 
cracking at the very spot which is level with the 
surface of the water; and sometimes the article 
will break asunder at that particular spot as evenly 
as though it had been cut with a saw. The tools 
required by the millwright, pattern-maker, carpen- 
ter, joiner, and cabinet-maker, are those kinds of 
tools which are generally attended with the greatest 
risk by being heated throughout their body, and 
only immersed half their depth into the water; 
especially the small and middle-sized varieties of 



HARDENING AND TEMPERING OF STEEL. 115 

the best kinds, which are always made wholly of 
the best cast steel, and which are generally filed or 
ground bright, and fitted to shape previous to hard- 
ening. The tools required by these different artists 
do not differ so much from each other in construc- 
tion and name as in size, though the very large 
tools used by millwrights, carpenters, and others 
for heavy, coarse work are generally composed of 
iron and steel welded together, the steel forming 
but a small portion of the whole mass of metal. 
With these kinds of large tools there is less risk 
of fracture in hardening, because it is generally 
shear steel or a mild kind of cast steel (steel con- 
taining a smaller proportion of carbon) which is 
used for welding to the iron. It is obvious that if 
the steel be properly welded to the iron, a flaw will 
be less likely to occur, and a rupture more difficult 
to start. 

From these statements the reader may, perhaps, 
be inclined to think that I am condemning the 
method which is so much practised in the art, that 
of partially dipping the articles and afterward tem- 
pering of them by the heat at the back of the tool 
or article ; but it is not my object to condemn a 
method which I know from experience to be in a 
considerable number of instances very convenient 
and very economical ; but knowing from experience, 
that certain kinds of articles are so liable to crack 
when the method of partially dipping them is 
adopted, I have made it my object to state the 
cause of their cracking, and to give such remedies 
as will, in a great measure, prevent these water 



116 HARDENING AND TEMPERING OF STEEL. 

cracks. "When the method of partially dipping a 
steel tool or other kind of article is adopted, the ar- 
ticle may generally be prevented from cracking by 
simply putting the water in motion previous to dip- 
pins; the article, or by giving the article a quick 
movement when it is in the water as far as it is re- 
quired hard ; either of these methods will prevent 
the water from acting so evenly in cooling it in a 
strict line ; either of these methods causes the line 
between the hard and soft part of the article to oc- 
cupy more space, and lessens the risk of fracture. 
Water-cracks may also be prevented in that part of 
any article which is required to be level with the 
surface of the water, by simply coiling a piece of 
binding wire round that particular part, and when 
sufficiently heated, coating it with the prussiate of 
potash previous to immersion. This method pre- 
vents the water from acting so suddenly or evenly 
upon the steel, at that particular part of the arti- 
cle ; consequently it prevents it cracking. 

Chipping-chisels, drills, and all other kinds of 
tools which are only partially dipped into the water, 
should never be held still while they are becoming 
cold ; but they should, after they are dipped to the 
required depth, have a sudden vertical or other 
movement given to them. I have no doubt that 
many have noticed when they have been chipping, 
that their chisels have sometimes broken off about 
an inch or rather more from the cuttinir-eda;e, or at 
that part of the chisel which was level with the sur- 
face of the water when it was hardeninff. The 
cause of the chisels breaking in this particular spot, 



HARDENING AND TEMPERING OF STEEL. 117 

arises in a great number of instances from the chis- 
els having been held quietly in the water when 
hardening. The water cooling them across in a 
straight line causes the hardened part to tear from 
the soft part ; and the chisels sometimes break with 
a very light blow of the hammer, and sometimes 
with the very first blow. I have, myself, wit- 
nessed the ends of drills drop off by simply dabbing 
their points into the wooden bench ; I have also 
witnessed the ends of drills drop off at the grind- 
ing-stone when they were being sharpened, after 
having been repaired ; I have also witnessed the 
ends of drills drop off on the slightest application to 
the work ; and from no other cause but from the 
drills having been held quietly in the water when 
hardening. But, as these kinds of articles are gen- 
erally hardened with the skin on the steel, they are 
less liable to break than articles which are bright- 
ened previous to hardening. I recollect once hav- 
ing a quantity of small flat drifts to harden, which 
had triangular grooves cut in them, to form sharp 
cutting-edges, something similar to a file,, but cut 
coarser and deeper, and I was requested to leave 
the top part of them (called the heads) soft. So I 
put a certain number of them into an iron box and 
surrounded them on all sides with charcoal dust ; 
after luting the box with clay, I placed it in a hol- 
low fire and slowly heated the whole to redness ; 
after which, I opened the box and let the contents 
drop from the box into the water-tank, with the in- 
tention of subsequently softening the heads. After 
taking them out of the water and examining them, 



118 HARDENING AND TEMPERING OF STEEL. 

I found a number of them very crooked ; this was 
owing to their being so slight and going from the 
box so suddenly into the water. As these kinds of 
tools are required for clearing, trueing, and finish- 
ing holes, it is obvious that this defect of being 
crooked is Yery detrimental ; for these tools cannot 
produce true work if they are crooked, besides, they 
are more liable to break when they are struck with 
the hammer than if they were straight. 

As the above method did. not afford a very satis- 
factory result, I adopted another method. I placed 
a certain number of them in a sheet-iron pan with- 
out a lid upon it; I surrounded the drifts with 
charcoal dust, the same as previously, and heated 
the whole to redness in a hollow fire ; as they 
became heated I gripped, separately the head of 
each drift with the pliers, and dipped it endways 
and perpendicularly and slowly into the water. This 
method had the effect of causing them to keep 
straight and answering the purpose so far, but it 
took a longer time to dip them separately; so, 
thinking to save this extra time, I thought I would 
only dip them in the water as far as they were 
required hard, and that would save the time and 
trouble of softening the parts which were not 
(according to order) to be made hard, namely, 
the heads of the drifts. But not caring about 
going ahead with any large quantity until I made 
myself sure that all was going on well, after I had 
dipped about two dozen of them, I thought it ne- 
cessary to examine them, and I did not find one of 
them but what was cracked at that part of the drift 



HARDENING AND TEMPERING OP STEEL. 119 

which was level with the surface of the water when 
hardening them ; so I dipped the remainder of them 
all over, and separately, and hardened them through- 
out, and not a crack appeared in one after. After 
tempering them to the proper temper, I made some 
lead red hot in an iron ladle and dipped the heads 
that were to be soft into it, and accomplished my 
object very nicely. 

This tearing of the particles from each other 
when the hardening terminates in a strict line is not 
at all times sufficient to cause the steel to break 
asunder, neither is it at all times sufficient to show 
signs of fracture; but whether the steel breaks 
asunder or not, or whether there are signs of frac- 
ture or not, this tearing of the particles from each 
other when the hardening terminates in a strict line, 
must always with highly carbonized steel more or 
less take place, when it is known that hardened 
steel occupies more space than soft steel, and that 
the density of the steel is different in the two states. 

"When it is required to harden large circular 
cutters which have teeth round their circumfer- 
ence, or large cutters having teeth on their sides as 
well as on their circumference, or, I may state, such 
cutters as those which have previously been treated 
of, they may be enclosed in a sheet-iron case or box 
and surrounded on all sides with either wood char- 
coal or animal charcoal. The box will require to 
be luted with clay or loam, and the whole placed in 
a furnace or hollow fire and heated to redness. A 
certain amount of time is essential to allow the steel 
to soak, or, in other words, to get heated uniformly 



120 HARDENING AND TEMPERING OF STEEL. 

throughout. After the cutters are properly heated 
they must be lifted out of the box separately, not. 
by the tongs or pliers, as they are apt to spoil the 
sharp cutting-edges of the cutter, but by a rod of 
iron (the poker) put through the spindle-hole of 
the cutter. The hardener must be provided with a 
proper tool for bearing the cutters while he dips 
them into the water, as the pliers do not answer well 
for this purpose. The most suitable tool for dipping 
the cutters is made by taking three pieces of round 
iron about one-quarter of an inch in diameter and 
three or four inches in length. Grip the three 
pieces at the end with the tongs and weld the three 
opposite ends together, after which the welded end 
must be scarfed and welded to the end of another 
piece of iron about one-quarter of an inch in diam- 
eter and about'eighteen inches in length ; this forms 
a stem with three prongs at one end of it. The 
three prongs must be turned back so as to stand at 
right angles with the stem ; so that when the stem 
is put through the spindle-hole of the cutter and 
gripped with the hand the cutter will lie upon the 
three prongs. A kind of ring or loop should be 
turned at the end of the stem to keep the stem from 
slipping through the hand by the weight of the cut- 
ter, but the loop must be sufficiently small to pass 
through the spindle-hole of the cutter. 

It may be inquired, will not a long bolt, with a 
large flat head, answer the same purpose as a stem 
with three prongs at the end of it ? The answer to 
this is : it would answer quite well as regards the 
bearing of the cutter, but the large flat head would 



HARDENING AND TEMPERING OF STEEL. 121 

prevent the water from passing freely through the 

spindle-hole of the cutter, and would thus prevent 

the cutter from cooling uniformly. After the cutter 

is lifted out of the box, this wire stem must be 

put through the spindle-hole of the cutter and 

gripped with the hand ; and while the cutter rests 

upon the three prongs it must be immersed into the 

water, and instead of moving the cutter backward 

and forward in the tank, it should be moved up 

and down so that fresh water is continually passing 

through the spindle-hole during the time the cutter 

is becoming cool. The deeper the tank the better 

it is for the purpose. Care must be taken whilst 

moving the cutter up not to allow it to come above 

the surface of the water, or it will be liable to crack. 

Should the tank not be sufficiently deep to allow 

moving the cutter up and down, the cutter may, 

after it is beneath the surface of the water, be turned 

sideways, and whilst one end of the wire stem is 

gripped with the right hand the opposite end can 

be gripped with the left hand. The cutter can 

easily, whilst it is beneath the surface of the water, 

be -shifted toward the middle of the wire stem, 

which will keep the cutter or the heated water as 

it passes through the spindle-hole of the cutter 

from burning the hands. It is advisable to keep 

the cutter moving until it is sufficiently cool to be 

gripped with the hand. If more than one cutter 

has been heated, the wire stem must be taken out 

of the water, as it will be required for dipping the 

other cutters. There is no necessity for removing 

the first cutter from the water until all the cutters 
6 



122 HARDENING AND TEMPERING OF STEEL. 

that have been heated have been immersed ; but, 
if the first cutter has increased the temperature of 
the water too high, more cold water should be 
added to it before the second cutter is immersed, 
and so forth, if necessary, until all that have been 
heated have been immersed. The cutters may, 
after they are hardened, either be allowed to remain 
in the water until the water is thoroughly cold, or 
they may be lifted out of the water by the method 
previously explained. If the cutters are uniformly 
heated and immersed in the water, in the manner 
just described, they will keep their proper shape 
better than by any other means ; while they are 
much less liable to crack, because they cool more 
uniformly. Any size cutters, dies, bushes, rings, or 
collars, or ring-gauges, may be heated and immersed 
in the water in the same manner as circular cut- 
ters. It will be obvious that gauges or dies which 
have no holes, or which have only a small hole 
through them, cannot be dipped with the same 
kind of tool as circular cutters, consequently the 
pliers will be quite suitable for gripping these kinds 
of articles. It is not absolutely necessary that cir- 
cular cutters, dies, bushes, rings, gauges, etc., should 
be enclosed in a box to heat them, neither is it abso- 
lutelv necessary to surround them on all sides with 
wood or animal charcoal, as it will answer equally 
as well, and be a far more expeditious method, to 
carefully and slowly heat them in the midst of the 
fuel of a hollow fire ; but when these kinds of arti- 
cles are heated for hardening in the midst of the 
fuel of a hollow fire, they should always be coated 



.HARDENING AND TEMPERING OF STEEL. 123 

with the prussiate of potash. Dies having en- 
graved surfaces are undoubtedly the better for being 
heated in a box and surrounded with wood or an- 
imal charcoal ; because it would not answer very- 
well to fill the fine engraving with the prussiate of 
potash, neither would it answer to heat them in 
contact with the air. The method of enclosing 
these kinds of articles in an iron box, and surround- 
ing them on all sides with wood or animal charcoal, 
answers three good purposes : it causes the heat to 
be very slowly and equally applied; the surfaces 
of the dies are rendered rather more steelly by the 
absorption of carbon, and it prevents the scaling oc- 
casioned by the contact of the air. If the dies or 
any other kind of steel articles be previously pol- 
ished, and well defended from the air, they will be, 
when hardened, nearly as clean as before. Small 
cutters, after they are hardened, require to be 
brightened in one, two, or more places, and tem- 
pered to a yellowish white or light straw color. A 
very good way of applying the heat for tempering 
most kinds of circular cutters is, to place the cutter 
upon a piece of round bar iron. The most suitable 
piece of iron for the purpose is made by slightly 
tapering several inches of a piece of round bar iron. 
The size of the iron, previous to drawing the taper 
upon it, should be a little larger in diameter than 
the diameter of the spindle-hole of the cutter ; so 
that, if it is necessary (whilst tempering the cutter) 
to draw the cutter upon the stouter part 9£ the iron, 
so that the iron may fit the hole tightly and supply 
more heat, it may be clone. To temper the cutters 



124 HARDENING AND TEMPERING- OF STEEL. 

by the use of this piece of iron, the tapered end of 
the iron will require to be heated to redness ; it 
must then be put into the spindle-hole of the cutter, 
the iron and the cutter must be supported with the 
left hand, whilst a slow rotary motion is given to 
the cutter, by the use of a small stick of wood, 
with the right hand. This method will equalize 
the heat, and cause the temper to be more uniform. 
As soon as the light straw color appears upon the 
brightened parts of the cutter, it must be removed 
from the heat ; after which it may be immersed 
either into water or oil, or it may be allowed to 
become cool in the air, for it matters not (after it is 
' removed from the heat) which way it becomes cool 
— that is, providing the heat has not been too sud- 
denly applied. Though this is the' most suitable 
method for applying the heat for tempering most 
kinds of circular cutters, still there are some kinds 
of circular cutters requiring to be tempered after 
they are hardened, where it will be found more 
convenient to temper them upon a piece of flat bar 
iron, heated to redness. The heat must not, in 
any instance, be too suddenly applied. It is ad- 
visable, in some instances, when tempering some 
kinds of circular cutters upon a piece of flat bar- 
iron, to place a piece of cold plate iron between the 
cutters and the red-hot bar, in order that the heat 
may be more slowly and equally applied. It will 
be found necessary, when tempering some kinds of 
circular cotters upon a piece of flat bar iron, to turn 
them over occasionally during the time they are be- 
coming heated, so as to epxose their opposite sides 



HARDENING AND TEMPERING- OF STEEL. 125 

to the heat, and thus impart to the cutter a more 
uniform temper. The yellowish white or light 
straw color gives tenacity to the steel without 
materially reducing its hardness ; it also lessens the 
risk of small cutters breaking when in use. There 
is no necessity for tempering or reducing the hard- 
ness of the largest size circular cutters ; because, 
owning to the larger body of steel, they are much 
longer than the smaller size cutters in becoming 
cool. A larger quantity of steam is also formed at 
the sides of the large cutters, which prevents the 
water, for a few moments, from acting upon the 
steel ; consequently, the largest size cutters cannot 
become so hard and brittle as the smaller size cut- 
ters. >The hardness, of course, depends, in some 
measure, upon the quality of the steel; likewise 
the temperature of the water and the temperature 
of the cutters when they are immersed in the water. 
If the quality of the steel, from which large and 
small cutters are made, be equal and if the temper- 
ature of the water in which the large and small 
cutters are immersed be equal also, and if the large 
and small cutters be equal in temperature when 
they are immersed, this variation in the hardness 
of the largest and smallest size circular cutters, for 
the reasons just given, must certainly take place. 
It will be obvious, then, that if the smallest size 
cutters require only to be reduced in temper to a 
yellowish white or light straw color, that the lar- 
gest size cutters will not, after hardening, require to 
be tempered ; but the hardening strain may be made 
more uniform throughout the body of large cutters 
by boiling them in water for several hours. 



126 HARDENING AND TEMPERING OF STEEL. 

Dies which have engraved surfaces, after they 
are hardened, require to be tenrpered ; not because 
the engraved surfaces of the dies are too hard, 
.but because the whole body of the steel requires to 
be toughened, in order to better fit the dies to with- 
stand the continual hardship to which they are 
generally exposed when in use. To temper these 
kinds of articles the engraved surface of the dies 
will require to be brightened ; the dies must then 
be placed upon a piece of flat bar iron, several 
inches of which must be heated to redness. If it is 
required to temper a quantity, several may be 
placed at once upon the bar. Care must be taken 
that all the dies may not arrive at the proper tem- 
per at the same moment. The dies should not be 
placed upon the hottest part of the bar at first; but 
they should, as they become gradually heated, be 
pushed upon the hotter part of the bar. The dies 
will require to be moved occasionally during the 
time they are becoming heated in order to equalize 
the heat. As soon as a light straw color appears 
upon the brightened surface of the dies, they must 
be removed from the hot iron ; and, if the heat has 
not been too suddenly applied to them, they may 
be allowed to cool in the air of their own accord. 
If the heat has been too suddenly applied, and has 
changed the under side of the die or dies to a deep 
blue color, it will then be requisite to cool them 
either in water or oil, otherwise the bottom side of 
the die, after it is removed from the hot iron, will 
continue to supply heat to the engraved surface 
and reduce the hardness too much ; and the die or 



HARDENING AND TEMPERING OF STEEL. 127 

dies will be practically useless for the purpose they 
are intended for, until the operations of hardening 
and tempering of them have been repeated. 

Hardening these hinds of articles a second time 
without hammering them increases the risk of their 
breaking ; and as they cannot be hammered with- 
out spoiling the engraving, it must be obvious that 
very' great care is required when hardening and 
tempering them, and the hardener ought never to 
place more of the dies upon the hot bar than what 
he can conveniently manage. 

When it is required to harden steel rings or col- 
lars which have one thick edge and one thin edge, 
such as the collars of some turning-lathes, these may 
be enclosed, several at once, in a sheet-iron case or 
box, and. surrounded on all sides with either wood 
or animal charcoal. The box will require to be 
luted with clay or loam, after which the whole may 
be placed in a furnace or hollow fire, and the steel- 
rings or collars heated to the proper temperature 
suitable for hardening them. To spare the trouble 
of enclosing these kinds of articles in a box and sur- 
rounding them with charcoal, they may be heated 
in a suitable furnace without being enclosed in a 
box, or they may be heated in the midst of the fuel 
of a hollow fire. When these kinds of articles are 
heated in a furnace or hollow fire in contact with 
air, and the fire free of wood or animal charcoal, 
they should always be coated, previous to immer- 
sion, with the prussiate of potash, in the manner 
previously explained. When the rings or collars 
arrive at the proper temperature suitable for hard- 



128 HARDENING AND TEMPERING OF STEEL. 

ening them, they must be drawn from the fire and 
placed upon the same or a similar kind of wire tool 
as that which is used for hearing circular cutters, 
whilst they are becoming cool when they are im- 
mersed in the water. The rings or collars may be 
immersed in the water separately, or two or three 
may be immersed at once, by taking care to place 
them upon the wire in such a position that the 
stoutest edge of each ring or collar may enter the 
water foremost. Previous to immersing these kinds 
of articles in the water, and when it is intended to 
place two or three of them at once upon the wire 
to be immersed together, it will be necessary to 
examine the depth of the water in the hardening 
tank, in order to ascertain whether the depth of the 
water is sufficient to allow the rings or collars when 
immersed being moved up and down without risk 
of bringing a part of the uppermost collar above 
the surface of the water. If the water is not suffi- 
ciently deep to allow these kinds of articles, when 
two or three are immersed together, being moved 
sufficiently to remove the heated water from the 
inside of them, it will be far better to immerse them 
separately, and thus lessen the risk of their break- 
ing. These kinds of articles require to be very slow- 
ly and uniformly heated, and should not be plunged 
too suddenly into the water. The more uniform 
the temperature the less liable are they to become 
oval or out of shape, and the more uniform they 
become cool the less liable are they to crack ; con- 
sequently it must readily be seen that these kinds of 
articles require to be immersed very slowly. It must 



HARDENING AND TEMPERING OF STEEL. 129 

also readily be seen that it is quite requisite that 
the thickest edge should enter the water foremost. 
The degree of heat required to harden these kinds 
of articles will, of course, depend upon the quality 
of the steel from which they are made. Sometimes 
rings and collars are made of the best cast steel ; 
they are made by punching a long hole near to the 
end of a steel bar ; after the hole is punched a 
round taper mandrel is driven into it to widen the 
hole ; it is then cut off the bar near to the hole and 
worked upon the beak-iron of the anvil.- When 
the ring or collar has nearly reached the proper 
form and size it is finished upon a larger mandrel 
than the first, after which it is annealed and turned 
in the turning-lathe to the required dimensions. 
When rings or collars are made of the best cast steel 
by the method here explained, they will onlv re- 
quire to be heated to a low red heat to harden 

them. 

Sometimes rings and collars are made of shear 

steel. They are made by scarfing the extreme end 
of a bar of shear steel ; the ring or collar is then 
partly formed by bending the scarfed end of the 
bar round the beak-iron of the anvil ; the partly- 
formed ring is then cut off the bar, and the second 
end is scarfed ; the two ends are then brought to- 
gether, and united by welding. The shear-steel 
rings are then finished upon a mandrel ; after which, 
they are annealed and turned in the lathe to the 
required dimensions. When rings or collars are 
made of shear steel by the method here explained, 

they will require to be heated to a bright cherry- 
6* 



130 HARDENING AND TEMPERING OF STEEL. 

red heat to harden them. Sometimes rings and 
collars are made of iron, and made to take the place 
of steel ; they are made in a similar manner as the 
shear-steel rings or collars. In order that the iron 
rings or collars may be made hard, and take the 
place of steel, they are, after they are finished being 
turned in the lathe with the exception of polishing, 
case-hardened. 

It is seldom necessary to temper or reduce the 
hardness of steel bushes, rings, or collars ; because 
the generality of these kinds of articles are required 
for bearings for different parts of machinery, where 
they have to endure a great amount of friction, con- 
sequently they require to be very hard to keep them 
from wearing. Eing and plug gauges, which are 
made of steel, require a great amount of hardness 
given to them to prevent them from wearing ; con- 
sequently these kinds of articles will not, after 
hardening, require to be tempered. 

Eing and plug gauges are sometimes made of 
iron, and made to take the place of steel by being 
case-hardened, previous to lapping or grinding to 
their proper sizes. The method of case-hardening 
will be explained in a subsequent chapter. 

It has already been shown, that the more uni- 
formly steel articles become cool when hardening, 
the less liable are they to fracture ; and it has been 
previously recommended that the stoutest part of 
steel articles should enter the water foremost. It 
becomes necessary, perhaps, to state here, that this 
method of immersing steel articles cannot in all in- 
stances be adopted ; for there are no means by which 



HARDENING AND TEMPERING OF STEEL. 131 

the stoutest part of some kinds of articles can be made 
to enter the water foremost. For instance, with 
such an article as a feather-edge circular cutter it is 
not practicable to get the stoutest part into the 
water first ; consequently, when this method can- 
not be adopted, some other which will have a ten- 
dency to cause the steel to cool uniformly must be 
resorted to. It will be obvious that the method 
of fitting a piece of flat iron to the thinnest 
part of this kind of article cannot conveniently 
be adopted. The process of concaving the sides 
to reduce the substance of the steel in that part 
of the cutter which is the last to become cool can- 
not be adopted, because this would unfit a feather- 
edge cutter for the purpose for which it is in- 
tended. It is evident then, that if none of these 
methods can be adopted with a feather-edge circular 
cutter that there is great risk of the largest kinds 
breaking from unequal cooling. When it is required 
to harden a large feather-edge circular cutter, it 
must be very slowly and uniformly heated to a 
cherry-red heat ; the most convenient way of heat- 
ing it is in the midst of the fuel of a hollow fire. 
As soon as the temperature of the cutter is sufficient 
to fuse the prussiate of potash, it must be taken out 
of the fire and coated with the potash, and then be 
returned to the fire for a few minutes, or until it ac- 
quires a cherry-reel heat ; after which it must be drawn 
out of the fire, and immersed in the water in a sim- 
ilar manner as other kinds of circular cutters. It will 
be obvious, from previous remarks, that if the tem- 
perature of these kinds of large cutters be properly 



182 HARDENING AND TEMPERING OF STEEL. 

regulated at first, they will not, after hardening, re- 
quire to be tempered. 

Previous to putting this kind of cutter into the 
fire, it will be well to cut out two rings from apiece 
of wire cloth and bind one of them upon each side 
and at the thin part of the cutter. Several short 
pieces of binding wire will be required for binding 
the wire rings upon the cutter. These wire rings 
will not prevent the thin part of the cutter from 
hardening, but if they be properly bound upon the 
cutter they will have a tendency to cause the potash 
to cling more firmly to it and prevent the water 
from acting too suddenly upon the thin part of the 
cutter, thereby causing it to cool more uniformly. 
It will not be necessary to bestow this trouble upon 
the smaller size cutters of a similar shape ; but, with 
large expensive cutters, to lessen the risk of fracture 
is not labor lost. 

It occurs to me, also, that the use of the wire 
rings may be dispensed with by taking a certain 
portion of the prussiate of potash and mixing with 
it a certain portion of flour or bean-meal, or some 
similar substance, and, after heating the cutter to 
redness, and giving it one coat with the pure prus- 
siate of potash, to give the thin part of the cutter a 
second coat with the mixture. If this mixture ad- 
heres to the thin part of the cutter it will prevent 
the water cooling it too suddenly, and thus prevent 
the cutter breaking ; but I have never given this 
mixture a trial myself, and cannot speak upon its 
value with certainty. 

When it is required to harden an eccentric ring 



HARDENING AND TEMPERING OE STEEL. 133 

or collar, it may be heated in the midst of the ig- 
nited fuel of a hollow fire. If it is made of the best 
cast steel it will require to be uniformly heated to 
a cherry-red heat and coated with the prussiate of 
potash in a similar manner as other articles, after 
which it must be immersed endways and perpen- 
dicularly in the water and entirely quenched. It 
will be obvious that there would be no difficulty in 
getting the stoutest part of such an article into the 
water foremost, but it will not answer to adopt this 
method in such a case. If the stoutest part were 
to enter the water foremost it would certainly cause 
the collar to cool more uniformly, and probably it 
would prevent the thinnest side of the collar break- 
ing ; but then, by going sideways into the water, it 
would cause the hole in the collar to become oval, 
and the outside of the collar to lose its proper shape, 
which would unlit it for the purpose for which it 
was intended ; consequently it is quite requisite 
that a piece of iron should be fitted to the thin side 
of the collar (as has previously been remarked), and 
that the collar should be immersed endways and 
perpendicularly in the water. 

When it is required to harden a large piece of 
round cast steel in which a hole has been bored 
through it (such a piece as has previously been 
spoken of), it may he surrounded with wood or 
animal charcoal in a sheet-iron box and heated 
either in a furnace or a hollow fire in a similar man- 
ner as other articles, or it may be heated in the 
midst of the ignited fuel of a hollow fire. If it is 
heated in the midst of the ignited fuel, it will re- 



134 HARDENING AND TEMPERING OF STEEL. 

quire to be coated with the prussiate of potash. 
Whichever method be adopted for heating it, it will 
require to be heated to a cherry-red heat, after 
which it must be withdrawn from the fire and placed 
upon the same kind of tool as that which is used for 
dipping circular cutters— it must be immersed end- 
ways and perpendicularly in the water. During 
the time it is becoming cool it must be moved up 
and down in the water in order to allow fresh water 
to pass through the hole, or, in other words, to re- 
move the heated water out of the hole ; or it may, 
after it is beneath the surface of the water, be turned 
upon its side and drawn backward and forward 
until it is cool. 

It may be inquired, What makes the difference 
whether the steel be moved about in the water dur- 
ing the time it is becoming cool, or whether it be 
held still, when it is known that heated water al- 
ways rises to the surface ? The answer to this is, 
that the heated water does not rise to the surface so 
suddenly as the heat is required to be extracted 
from the inside of the article ; consequently, it is 
quite requisite that it should be moved about in the 
water in order that the cooler portions of the water 
may pass through the hole and cool the article more 
uniformly. 

It has previously been stated that it is injurious 
to bore holes too near to the outside edges of steel 
articles ; but it is obvious that boring holes near to 
the edges cannot, with some kinds of articles, be 
avoided ; therefore, if the hardener is required to 
harden any kind of steel article which has holes in 



HARDENING- AND TEMPERING OF STEEL. 135 

it near to the edges, it is advisable before putting 
the article in the tire to stop the holes with a piece 
of loam : this method will prevent the steel break- 
ing at the holes. It may be useful to some who are 
not much accustomed to harden steel to know that 
if a piece of binding- wire be wrapped round any 
part of a steel article, and a piece of loam wrapped 
round the wire, it will prevent the steel from hard- 
ening in that part when it is immersed in the water ; 
consequently it will prevent the steel breaking at 
the part where the loam is on. The wire is for no 
other purpose but to prevent the loam from falling 
off; the loam requires to be dried upon the article 
before it is put into the fire, otherwise it will prob- 
ably crack and let the water get at the steel. But, 
for the sake of making this subject properly under- 
stood, as it may often prove very useful to the hard- 
ener, let us suppose that the middle part of a 
piece of one inch square cast steel is required to be 
hardened and the two ends required to be kept soft. 
We will suppose it to be four inches in length, and 
at each end of it a countersunk round hole, for the 
reception of a bolt three-eighths of an inch in diam- 
eter, having a cheese-shaped head three-eighths of 
an inch in thickness, and three-quarters of an inch 
in diameter. 

It must easily be seen, by the shape of this kind 
of article, that if a proper method is not adopted 
there will be some difficulty in hardening it to make 
it answer the requirement, namely, quite hard in the 
middle and soft at the ends, and not cracked at the 
holes. If this kind of article could be made hot in 



136 HARDENING AND TEMPERING OF STEEL. 

the middle without heating the two ends there 
would be an end to the difficulty ; but it is obvious 
that, owing to the shortness of this kind of article, 
this cannot be done, so that, whatever method be 
adopted in heating it for hardening, it will require to 
be heated throughout its body. Fires are sometimes 
made so that a very short heat may be got upon any 
part of some kinds of articles ; but this is an article 
which will require a certain amount of time to soak, 
consequently the middle part of it cannot be prop- 
erly heated in a short open fire without the two ends 
becoming hot : it is evident, then, that the article 
must be heated throughout its body. There are 
various methods that could be adopted in hardening 
this kind of article. First, it may be heated in an 
iron box in contact with charcoal, or it may be heat- 
ed in the midst of the ignited fuel of a hollow fire ; 
when it is sufficiently heated it may be lifted out of 
the fire with the pliers ; one end of it must then be 
dipped into the water and partially cooled, after 
which the opposite end must be dipped and partial- 
ly cooled in a similar manner. This operation is to 
partly cool the steel to keep it from hardening at 
the parts which are required soft. 

When the temperature of the two ends is re- 
duced beyond that which will harden the steel, the 
whole of the article must be immersed in the water 
and entirely quench ed. A certain amount of dexterity 
is required in cooling the ends, otherwise the middle 
part of the article which is required hard will be- 
come too low in temperature to harden properly. 
By adopting this method, the middle part of the 



HARDENING AND TEMPERING OF STEEL. 137 

article is hardened and the ends remain soft. Still 
this method is not perfect ; because the article fre- 
quently becomes cracked at the holes when cooling 
the ends. 

Another method of hardening this kind of arti- 
cle is to heat it the same as before, and immerse it 
at once in the water. This, of course, hardens the 
ends as well as the middle. The ends may subse- 
quently be softened, though very imperfectly, by 
placing them between pieces of iron heated to white- 
ness ; or the heat may be more suddenly applied by 
punching a hole (the size and shape of the end of 
the article) in two separate pieces of stout iron, and, 
after heating the two pieces of iron to a whitish 
heat, placing the ends of the article into the holes. 
This method of hardening this kind of article is 
not perfect ; because the article is liable to become 
cracked at the holes in hardening, and the hardness 
is liable to become reduced in the middle of the 
articles by heating the ends to get them soft. 

Another method is to heat the article in a hollow 
fire and harden it throughout, after which the two 
ends may be made soft by dipping them, one at a 
time, in some red-hot lead. This method is not per- 
fect, because the article is liable to become cracked 
at the holes in hardening, and too much time is re- 
quired for heating the lead for softening the ends ; 
and, as time is money, this becomes a very expensive 
way. Though red-hot lead is an excellent thing for 
heating some articles, and would answer quite well 
for softening the ends of this kind still it is quite 
unnecessary to make use of it in this instance. 



138 HARDENING AND TEMPERING OF STEEL. 

The most convenient and satisfactory method of 
hardening this kind of article, is to wrap a piece of 
binding-wire about the holes, and then to fill the 
holes with loam, at the same time cover the ends 
and the wire with the loam ; this will form a small 
ball of loam at each end of the article ; the wire is 
to prevent the loam falling off. After the loam is 
placed upon the ends it will require to be gradually 
dried before it is put into the fire ; after the loam has 
become dry the article may be placed in the midst 
of the heated fuel of a hollow fire ; that part of the 
article which is not covered with the loam will require 
to be coated with the prussiate of potash ; the potash 
may be put on without drawing the article out of the 
fire by using a slip of iron, one end of which should 
be the shape of a spoon ; the article will require to 
be heated throughout to a cherry-red heat, after 
which it must be drawn out of the fire and immersed 
in the water and entirely quenched. Those parts of 
the article which are surrounded with the loam, 
namely, the holes, will remain soft and will not 
crack, because the water cannot penetrate through 
the loam quick enough to harden the steel. I have 
myself had numbers of articles to harden similar 
in shape to the one just described, and by adopting 
the method of stopping up and surrounding the 
countersunk holes with the loam I never knew one 
to crack ; though I have seen numbers of the same 
kind of articles cracked at the holes when the loam 
has not been used. It may be imagined, perhaps, 
that, if one method were given for hardening this 
kind of article it would have been sufficient : but I 



HARDENING AND TEMPERING- OF STEEL. 139 

have thought it necessary to mention various meth- 
ods (at the same time I have stated which is the best 
method) in order that it may set the young me- 
chanic thinking, and to afford him a better oppor- 
tunity of judging for himself which is the best 

method. 

It has previously been stated that sharp inter- 
nal angles are unfavorable to articles which require 
to be hardened, and it has been hinted that sharp 
internal angles should be avoided ; but, as they are 
required in some kinds of articles, and as they are 
often left in articles when they are not required in 
them, I will state that, when I have an article 
to harden which has sharp internal angles, I always 
bind a piece of binding-wire in the angles of the 
articles, and when I have a circular cutter to hard- 
en, which has a flat key-way in it with sharp an- 
gles, I always make a kind of key, by bending a 
piece of binding-wire backward and forward and 
then bind it into the key-way of the cutter. This 
of course does not strengthen the cutter, but it has 
a tendency to cause the potash to cling more firmly 
at the key-way, and prevents the water acting too 
suddenly upon the weakest part of the cutter. It 
may, perhaps, be thought by some that it will be 
better to fit an iron key into it ; if an iron key were 
fitted tight into it, it would have a tendency, at the 
period when the cutter was shrinking from the hot 
to the cold state, to split it, as the cutter would 
have to compress the key, which would hold it for 
the moment in a greater state of tension (strain) 
than if the key were not there. 



140 HARDENING AND TEMPERING OF STEEL. 

It has previously been stated that it is injurious 
to make the centres too deep or too large in some 
kinds of articles which require to be hardened ; 
consequently, it will be well to remark here, that, 
if the hardener meet with articles that he considers 
have too large a centre in them, it will be well to 
stop up their centres with a piece of loam previous 
to hardeuing, and thus prevent them becoming 
cracked at the centres in hardening. 

When it is required to harden a large quantity 
of small or medium size screw-taps at once, they 
may be enclosed in a sheet-iron case or box, and 
surrounded on all sides with either wood charcoal 
or animal charcoal. Preference should be given to 
the wood charcoal on account of it undergoing no 
change by being exposed to heat, providing the 
access of air is prevented ; consequently, it can be 
saved and put aside to be used again. The taps 
will require, of course, to be packed in alternate 
layers, commencing with the charcoal on the bot- 
tom of the box, to the thickness of about three- 
quarters of an inch, and finishing with a layer 
about the thickness of the first; the intermediate 
layers of the charcoal need not be more than one- 
third the thickness of the first and last layers. Suf- 
ficient space must be left every way for the expan- 
sion of the steel taps by the heat ; otherwise, as 
they become heated, they will bend and damage 
each other. After the packing is completed and 
the lid of the box put on, it will require to be luted 
with clay or loam (in order to exclude the atmos- 
pheric air), after which, the box and its contents 



HARDENING AND TEMPERING OF STEEL. 14:1 

must be placed in a suitable furnace or hollow fire, 
and the whole heated to a cherry-red heat. The 
fire must not be urged, as a certain amount of time 
is essential to allow the contents of the box to 
become uniformlv heated throughout. When the 
whole arrives at the proper heat, the box may be 
drawn to the mouth of the fire, the lid removed, 
and each tap taken out separately and immersed 
endways (screw end foremost) and perpendicularly 
in the water ; or the box may be drawn out of the 
fire, and the whole of the taps immersed at once 
direct from the box in the water. It is obvious 
that it is a more expeditious way of hardening to 
immerse them all at once. But then they are more 
likely to become crooked than if they were taken 
out of the box separately, and immersed perpendic- 
ularly and slowly into the water. If the harden- 
ing tank is made of iron, and the method of im- 
mersing the whole of the taps at once is adopted, it 
will be well to sink a piece of board to the bottom 
of the tank for the taps to fall upon ; the board 
should be nearly the length and width of the inside 
of the tank, and may be sunk by placing a piece 
of iron upon each end of it. If, in addition to this, 
a piece of iron or a brick be placed at each end, be- 
neath the board, it will have a tendency to cause 
the board to spring and scatter the taps when they 
are tipped out of the box, which will cause them to 
cool more equally. The taps will of course require 
to be packed in such a position that they will, 
when the box is held over the hardening tank, fall 
endways and perpendicularly into the water. 



142 HARDENING AND TEMPERING OE STEEL. 

When it is required to harden a largo quantity of 
the largest size screw-taps, they may be enclosed' in 
an iron box, and surrounded with carbon in a simi- 
lar manner as the smaller sizes. They must not, 
like the smaller taps, be allowed to fall direct from 
the box into the water, but must be taken out of 
the box and immersed separately ; but it will be a 
more expeditious way to heat the largest size taps 
in the midst of the ignited fuel of a hollow fire, or 
a suitable furnace. If this method is adopted, the 
taps will require to be very slowly heated ; but 
several may be heated at once. When they arrive 
at a cherry-red heat, which is the heat suitable for 
hardening them, they must be taken out of the fire 
separately and coated with the prussiate of potash, 
after which they must be returned to the fire for a 
few minutes, or until they regain the heat lost 
while being coated ; after which they must be 
taken out and immersed endways, screw end fore- 
most, and perpendicularly in the water. This 
method of applying the heat may also be adopted 
with small quantities of small or middle-size taps. 
Taps hardened by this method will answer the pur- 
pose for which they are intended equally as well as 
if they were heated in a box surrounded with car- 
bon. 

In all cases the taps must be allowed to remain 
in the water until they become quite cool, after 
which, when taken out, and previous to using them, 
they will require to be tempered ; but before tem- 
pering they must be brightened in one, two, or more 
places, in order that the color may be seen, and the 



HARDENING AND TEMPERING OF STEEL. 143 

proper, temper ascertained. It will not be necessary 
to brighten the square tops or heads, but only the 
plain round parts of the taps, also one of the con- 
cave grooves which are cut along the side of the 
taps. After the taps are brightened, they may be 
tempered by exposing them again to heat, When 
a large, quantity is required to be tempered, place 
as many of the taps at once as may be convenient 
into an oven or gas-stove specially constructed; 
heat the taps until a dark straw color appears upon 
the surface of them. This temper is the best that 
can be given to screw-taps which are required for 
general purposes, but those required for a special 
purpose, such as cutting hard cast iron, or some 
kinds of steel, will then require to be tempered to 
a yellowish-white or light straw color. As soon as 
the proper color appears upon the surface of the 
taps, they mnst be withdrawn from the heat. If 
the color does not further change after the taps are 
withdrawn from the heat, it is a proof that the heat 
has not been too suddenly applied ; and the taps 
may then be cooled in oil, or they may be allowed 
to become cool in the air of their own accord. 
Should the color be observed to be changing from 
a straw color to a golden color, the taps must in- 
stantly be cooled in water ; otherwise they will be- 
come too soft for the purpose for which they are 
intended. Cooling the taps in oil, after they are 
tempered to the proper color, has a tendency to 
prevent them rusting if they are laid aside. The 
greater portion of the oil, of course, will require to 
be wiped off; but the taps need not be wiped quite 



14:4: HARDENING AND TEMPEEING OF STEEL. 

dry. Another method by which screw-taps may 
be tempered, is to place a piece of plate iron into 
and near to the month of any common furnace, such 
as those which are connected with steam-boilers, 
etc. After the plate is placed in the furnace several 
of the taps may be placed at once upon the plate, 
and heated until the proper color appears. The 
taps will require to be moved about upon the plate 
during the process in order to equalize the heat. 
As they become heated, and the proper color ap- 
pears upon their surfaces, they must be withdrawn 
from the heat ; their places may be filled up with 
others, and a Continuance of the process may be, if 
necessary, kept up. It is not every person who 
makes screw-taps that has large quantities to tem- 
per at one time, so as to require a furnace, or oven, 
or gas-stove. The amateur mechanic seldom has 
more than two or three sets at most requiring to be 
tempered at one time. There are others who have 
only a few to temper occasionally, merely for the 
use of the shop; consequently, it may be well 
to explain another convenient method whereby 
a small quantity of screw-taps may be tempered 
without the use of the furnace, oven, or gas-stove. 
A small quantity of taps, after they are hardened 
and brightened, may be tempered by gripping the 
top of the taps, one at a time, with a pair of tongs, 
and holding them in the inside of an iron ring, 
heated to redness, until a dark straw color appears 
upon its surface. The heated ring may be placed 
upon the anvil or other suitable place.. The screw 
end of the tap must be allowed to project out of the 



- 
HARDENING- AND TEMPERING OF STEEL. 145 

ring when first the heat is applied, otherwise the 
point of the tap, or the leading thread, will change 
its color sooner than the middle part of the tap, and 
the temper will be unequal. As the top or plain 
part of the tap changes its color, the screw part 
must be drawn back into the ring. If the jaws of 
the tongs by which the tap is gripped be previously 
heated to redness, it will be the better, as the heated 
tongs will help to supply heat, and temper the taps 
more uniformly. It will be obvious that if the top 
or plain parts of small screw-taps be tempered to a 
blue, that they will be less likely to break when in 
use ; consequently, the heated tongs will be very 
convenient for tempering the plain parts of the taps 
to a blue at the time that the screw part is being 
tempered to a straw color. The hardener ought to 
be provided with two rings and three pair of tongs, 
so that, whilst one heated ring and one pair of 
heated tongs are being used, the other ring and 
another pair of tongs may be in the fire becoming 
heated. The third pair of tongs should not be 
heated, but they should be ready at hand ; so that, 
if it should happen that the heated tongs supplied 
the heat too suddenly to either of the taps, the 
heated tongs could be laid aside for a few minutes, 
and the tap gripped with the cold pair of tongs. 
With care, two, and sometimes three of the small- 
est or the middle size taps may be tempered with- 
out reheating the ring. The larger the diameter 
of the tap, the longer it will be in changing its 
color, that is, providing the heat is properly ap- 
plied. The thickness of the iron from which the 
1 



146 HARDENING AND TEMPERING OP STEEL. 

ring requires to be made must be in proportion to 
the thickness of the tap ; or, in other words, the 
larger the diameter of the tap the thicker the ring 
will require to be, in order that the ring may retain 
sufficient heat long enough to temper the tap. The 
diameter of the inside of the ring will require to be 
about two inches larger than the diameter of the 
tap. If smaller than this, it will be apt to supply 
the heat too suddenly to the tap. The length of 
the ring will require to be about the same length 
as the tap, except when the ring is required for 
tempering very long tapered taps, such as those 
sometimes required to have the screw part as much 
as five, six, or more inches in length. When the 
ring is required for tempering these kinds of taps, 
it will be more convenient to have it somewhat 
shorter than the tap, and move the tap to and fro 
in the ring;. 

The hardener will find in practice that if two 
or three short rings be heated and placed in a line 
with each other, and made to take the place of a 
long single ring, it will be more convenient for tem- 
pering these kinds of taps. 

Screw-taps are sometimes required for some 
purposes as much as eighteen and more inches in 
length, the screw part occupying but a small por- 
tion (about three inches) of the whole length of the 
taps. When it is required to harden these kinds 
of taps, they may be placed in the midst of the 
ignited fuel of a very small hollow fire ; or they 
may be placed in the inside of a piece of iron pipe, 
the iron pipe being previously placed in the midst 



HARDENING AND TEMPERING OF STEEL. 147 

of the fuel of an open fire. The screw part of 
these kinds of taps is the only part which requires 
to be hardened ; consequently, it is the only part 
necessary to be heated. They must be very slowly 
and uniformly heated to a cherry -red heat, and im- 
mersed endways and perpendicularly in the water 
and entirely quenched. These kinds of taps will, 
like the other kinds, require to be brightened and 
tempered. The plan of applying the heat by the 
use of an iron ring will be very convenient, but the 
method of gripping the taps with the heated jaws 
of a pair of tongs, it will be obvious, cannot con- 
veniently be adopted ; consequently, if they be stout 
taps, a very thick ring heated to whiteness will be 
required. The whole of the screw part, and about 
one inch and a half of the plain part of the tap, 
must be allowed to project out of the heated ring, 
in order that the heat may be applied to a certain 
portion of the plain part of the tap first ; otherwise 
the tap cannot be properly tempered. This part 
of these kinds of taps requires to be in contact with 
a greater amount of heat than will at first sight be 
readily imagined, and it is for this reason that I 
have suggested a very hot ring. If the diameter 
of the inside of the ring be somewhat smaller for 
these kinds of taps than for other kinds, it will not 
be amiss. As soon as this part of the tap (which 
is in the ring) has changed its color to any of the 
intermediate colors between a light straw and a 
deep blue, the screw part of the tap which is now 
projecting out of the ring must be drawn back into 



148 HARDENING AND TEMPERING OF STEEL. 

the ring, and tempered to the same color as other 
kinds of taps, namely, a dark straw color. 

"When it is required to harden master-taps (com- 
monly called by workmen, hobbs), the same meth- ' 
ods adopted with other kinds of taps must be ap- 
plied, with the exception that these kinds of taps 
must be left, in a slight degree, harder than the 
other kinds. The reason for this is, they are mostly 
required for cutting steel, such as the threads of 
screw-dies, also for cutting the threads upon those 
kinds of screw-tools called chasers, etc. ; conse- 
quently the small and middle size master-taps will 
not require to be reduced in temper lower than a 
yellowish white or light straw color. It will be ob- 
vious from the manner in which master-taps are 
grooved, that there is greater liability of their break- 
ing in hardening, and less liability of their breaking 
when in use, than the other kinds' of taps of the 
same diameter; consequently, when it is required 
to harden the largest size master-taps, the heat 
should be carefully regulated at first, so that, after 
they are immersed in water, become cool, and taken 
out, they will be ready for use,' and thus dispense 
with the subsequent process of tempering. The 
largest size master-taps will be the better (whether 
heated surrounded with carbon in an iron box, or 
whether heated in the midst of the fuel of a hollow 
fire) if they are coated with the prussiate of potash 
previous to immersion. 

When it is required to harden large or small 
screw-dies, in large or small quantities, they may 
be heated in a similar manner as screw-taps, either 



HARDENING AND TEMPERING OF STEEL. 149 

by enclosing them in an iron box and surrounding 
them on all sides with, carbon, and placing the 
whole in a furnace, or by placing them in the midst 
of the ignited fuel of a hollow fire. Whichever 
method is adopted, they will require to be uniformly 
heated to a cherry-red heat. They will require to 
be immersed plain end foremost in the water ; or, 
in other words, the screw part of the dies should be 
uppermost when the dies enter the water. It will 
be obvious that, if the dies are immersed separately, 
there will be no difficulty in making the plain end 
of them enter the water foremost ; but in order to 
approach this method as near as practicable, the 
dies should be packed in the box in such a position 
that they will all have a tendency (when the box is 
opened and held over the water-tank) to fall plain 
end foremost into the water. When the dies are 
heated in the midst of the ignited fuel of a hollow 
fire, they will require to be coated with the prus- 
siate of potash previous to immersion. A very 
convenient box in which to heat a moderate quan- 
tity of small screw-dies or small screw-taps, may 
be made by welding a plug into the end of a piece 
of large wrought-iron pipe. A loose plug will be 
required for the opposite end of the pipe; it must 
be the same size as the bore of the pipe, and about 
one inch and a half in length. Part of the plug 
must be allowed to project out of the pipe for the 
convenience of gripping it with the tongs, or tap- 
ping it with the hammer when required to be taken 
out ; otherwise, it may be difficult to get it out, 
especially after it has been luted with loam. The 



150 HARDENING AND TEMPERING OF STEEL. 

plug will require to be temporarily fastened into 
its place ; this maybe done by boring a hole through 
the pipe and the plug, and driving an iron pin 
through the two. It will be obvious that when a 
large quantity of screw-dies or screw-taps are re- 
quired to be heated in a box, the box should be 
larger in proportion to the quantity to be operated 
upon, and the box will require to be made of plate 
iron. 

After screw-dies are hardened, they will require 
to be brightened and tempered. The tempering may 
be performed by placing the dies, several at once, 
upon a hot plate of cast metal ; or they may be tem- 
pered by placing them upon a piece of bar iron, one 
end of which must be heated to redness. Those 
hinds of dies which are used in the screwing ma- 
chine, and all large screw-dies of a similar shape, 
will require to be placed upon the heated iron, screw 
part uppermost, in order that the heat may not be 
too suddenly applied to the cutting part of the dies. 

As soon as these kinds of dies are observed to 
be changing their color, they must be moved to the 
cooler part of the iron, otherwise the bottom part of 
the screw part of the dies will be apt to become softer 
than the top part, and the temper would be un- 
equal. It will sometimes be found necessary, after 
the dies are removed to the cooler part of the iron, 
to turn them bottom upward for a few moments, or 
to turn them upon their sides, in order to obtain a 
uniform degree of temper. 

Some kinds of screw-dies require to be placed 
upon the hottest part of the iron at first, and as they 



HARDENING AND TEMPERING OF STEEL. 151 

become heated should be drawn toward the cooler 
part of the iron. Other kinds of screw dies require 
to be placed upon the cooler part of the iron at first ; 
and, as they become heated, they require to be drawn 
toward the hotter part of the iron. This, of course, 
depends upon the depth of the dies, or the distance 
between the screw part and the back part of the 
dies. 

The dies must be allowed to remain upon the 
heated iron until their cutting parts become uniform- 
ly changed to a dark straw color ; after which they 
may be cooled in water or oil, or allowed to cool in 
the air of their own accord, according to circum- 
stances previously explained. The smaller size screw- 
dies may be uniformly tempered, and the heat very 
gradually applied, by placing them upon a stout 
piece of cold plate iron, and then placing the plate 
and dies upon a thick piece of iron heated to a 
whitish heat. The dies must be turned over occa- 
sionally in order to expose all their sides to the heat. 
As their surfaces become changed to a dark straw 
color, they may be pushed off the plate into a vessel 
containing water or oil. If the plate has not become 
too hot, their places may be filled up with others. 
If the plate has become too hot, it may be taken off 
the hot iron and placed upon the anvil face ; it will 
then in a few moments be in a fit state for temper- 
ing a second quantity. By putting the plate back 
into its place (upon the hot iron) a third, and some- 
times a fourth quantity, may be tempered without 
reheating the iron. 

When it is required to harden a large quantity 



152 HARDENING AND TEMPERING OF STEEL. 

of those kinds of screw-tools . called chasers, they 
may be placed (several at once, or as many as may 
be convenient), in the midst of the ignited fuel of an 
open fire, or they may be placed in the midst of the 
ignited fuel of a very small hollowflre. The screw end 
or cutting part of the chasers requires to be heated to 
a cherry-red heat. The blast, of course, must be spar- 
ingly used. When they arrive at the proper heat, they 
must be drawn out of the fire ; but, should there be 
some in advance of the others, these must be the 
first to be drawn out, after which the heated end 
will require to be coated with the prussiate of pot- 
ash. They must then be returned to the fire for a 
few minutes, or until they acquire a cherry-red heat, 
after which they must be immersed into the water 
and entirely quenched. In order to keep up a con- 
tinuance of the process, as they are withdrawn their 
places in tlib fire must be filled up with others. 
After the whole of them have been immersed and 
become cool, they will require to be brightened and 
tempered. They may be brightened upon a grind- 
ing-stone or an emery-wheel, or by rubbing the top 
surface with a piece of grinding-stone, or by an 
emery stick, or a piece of emery cloth. After the 
chasers are brightened they may be placed, several 
at once, upon a piece of flat bar iron heated to red- 
ness. The screw end of the chasers must be allowed 
to project some distance (about one inch and a 
quarter) over the heated iron, otherwise the heat 
will be too suddenly applied to the cutting parts of 
the chasers. As soon as a yellowish- white or light 
straw color appears upon the cutting parts of the 



HARDENING AND TEMPERING OF STEEL. 153 

chasers, they must be removed from the heat and 
cooled' in water or oil, otherwise the hack part of 
the chasers which was in contact with the heated iron 
will continue to supply heat, and the chasers will 
become too soft. As the chasers are removed from 
the hot iron, their places can be filled up with oth- 
ers. By having two pieces of iron, one piece in the 
fire becoming heated whilst the other piece is being 
used, a continuance of the process may be kept up. 
After the chasers are taken out of the water or oil, 
and the top surface ground upon the grinding-stone, 
they are ready for use. Though this method is a 
very expeditious one for hardening and tempering 
a large quantity, still it is not absolutely necessary 
to adopt it with a small quantity, or a single 
chaser ; because they may with care be hardened 
and tempered equally as well by heating them 
and partially dipping them into the water and 
tempering them by the heat at the back part of the 
chaser, without the use of the hot iron. It will be 
obvious that, when this method is adopted, a great- 
er portion of the tool will require to be heated, in 
order that the back part of the chaser may retain 
sufficient heat to temper the cutting part after it 
has been immersed into the water. 

When this method of partially dipping the 
chaser is adopted, it will be advisable to put the 
water in motion previous to dipping the chaser ; or, 
otherwise, when the cutting part of the chaser is 
beneath the surface of the water, give the chaser a 
quick movement ; this will prevent the water from 

cooling the steel in a strict line, and guard against 
7* 



154 HARDENING AND TEMPERING OP STEEL. 

water-cracks. That part of the chaser which is be- 
neath the surface of the water must be allowed to 
remain in the water until it becomes quite cool, 
after which it must be taken out and brightened. 
In a short time the back part of the chaser will 
supply sufficient heat to the cutting part to temper 
it to the desired color. As soon as the proper color 
appears, the chaser must be entirely quenched ; 
and, when taken out of the water and ground upon 
the grinding-stone, it will be like those which have 
been wholly quenched and subsequently tempered 
on the heated iron, ready for use. 

When it is required to harden a screw-plate, it 
may be placed in the midst of the ignited fuel of a 
very small hollow fire, or among the ignited fuel 
of an open fire. It well require to be very slowly 
and uniformly heated to a cherry-red heat ; the 
blast of course must be sparingly used, otherwise it 
will become crooked. There is no necessity for 
heating the whole length of the shank or handle; 
but it is quite necessary to heat a small portion of 
it, in order to obtain a more uniform heat upon the 
plate. As soon as the temperature of the plate is 
sufficient to fuse the prussiate of potash, it must be 
withdrawn from the fire, and coated with the pot- 
ash, in a manner similar to other kinds of tools ; 
after which it must be immersed very slowly, end- 
ways and perpendicularly, in water. The largest 
size screw-plates will generally keep truer by being 
immersed edgeways and horizontally in the water. 
The screw-plate must be allowed to remain in the 
water until it becomes quite cool, after which, 



HARDENING AND TEMPERING OF STEEL. 155 

when taken out, it will require to be brightened 
and tempered. It may be tempered by holding it 
over a piece of flat bar iron (heated to redness), 
until a dark straw color appears upon its surface ; 
or it may be tempered between two pieces of flat 
iron heated to redness, and placed a certain distance 
apart from each other, in order that the heat may 
not be too suddenly applied ; or it may be held in 
the inside of an iron ring heated to redness ; or it 
may be tempered in a sand-bath, provided the tem- 
perature of the sand is just sufficient to change it 
to the proper color — if the sand is hotter than this, 
there is a great risk of the threads becoming too 
soft ; or the heat may be applied by any other con- 
venient method, after which the plate will be ready 
for use. 

Screw-plates and screw-dies are often ruined by 
being used upon iron and steel rough from the 
forge, and covered with scales, which, from their 
hard, gritty nature, grind away the threads. In all 
cases the rough scale should be removed from the 
iron or steel, either by the turning-tool, file, or 
grinding-stone, previous to screwing it with the 
screw-plate or the dies. It is not an uncommon 
practice with some workmen, after they have fin- 
ished forging a piece of iron-work, and whilst the 
iron is at a red heat, to immerse it in water and 
partly cool it, with a view of giving the work a 
cleaner appearance ; but this is a very bad cus- 
tom, especially when the forging requires to be 
screwed. It very often happens that the iron 
contains veins of steel, which harden by immer- 



15G HARDENING- AND TEMPERING OF STEEL. 

sion ; and, though the metal may not be so hard 
as to prevent its being cut with a hard turning- 
tool, still, when it comes to be screwed with the 
stocks and dies, or with the dies belonging to 
the screwing-machine, or with the screw-plates 
(which tools are always less hard than the turning- 
tools), it will spoil the dies or the screw-plates; 
and because this hard place or places do not happen 
to be detected when turning the work (on account 
of using a very hard tool), the steel the dies or 
screw-plate is made of will be thought bad, or badly 
tempered. The fact is, the work should always be 
annealed rather than hardened. In all cases when 
an impure iron is made use of for forgings, and. 
which will subsequently require to be screwed, 
either with the screw-dies or the screw-plate, or 
which may require to be cut with circular cutters 
or with circular saws, the forgings should always 
be annealed previous to leaving the smithy. The 
forgings, of course, will be the better for being an- 
nealed supposing they are to be screwed with the 
screw-tools belonging to the turning-lathe ; though 
it is not of so much importance as when they are to 
be screwed with the dies, or the screw-plate, or cut 
with circular cutters, or circular saws, because the 
screw-tools belonging to the turning-lathe can be 
ground again, provided they chip from being very 
hard ; whereas, the generality of screw-dies, screw- 
plates, and circular cutters, and even circular saws, 
when very hard, and once spoilt, will not admit of 
being again sharpened, but will be practically use- 
less, until they have been annealed, and cut up 



HARDENING AND TEMPERING OF STEEL. 157 

again, and subsequently hardened. Annealing 
makes the iron more uniform in temper, and will 
save much subsequent trouble ; it will greatly fa- 
cilitate the work when fitting it up. 

When it is required to harden a large quantity 
of stout circular saws at once (for cutting metals), 
they may be eDclosed in a sheet-iron case, or box; 
they will require to be surrounded on all sides with 
either wood or animal charcoal. Sufficient space 
must, of course, be left every way for the expansion 
of the saws ; otherwise they will become buckled in 
heating. After the saws are enclosed and the box 
luted with clay or loam, the whole may be placed 
in a suitable furnace or hollow fire and the saws 
heated to a cherry-red heat (the fire of course must 
not be urged.) As soon as the whole arrive at the 
proper uniform temperature, the box must be drawn 
toward the mouth of the fire, the lid taken off and 
the saws taken out separately. They may either be 
taken out of the box with the pliers or by a small 
rod of iron, having a small hook turned upon one 
end of it. The saws will require to be immersed 
edgeways in a trough containing water, the surface 
of which must be covered with a film of oil. The 
oil will float of itself upon the surface of the water 
and burn upon the saw as it passes through it. 
The burnt oil forms a coating of coal upon the saw, 
which protects it from the direct action of the water, 
and lessens the risk of fracture. 

Though saws are the better for being enclosed in 
a box and surrounded with charcoal when heating 
them, still, when a single saw is required to be 



158 HARDENING AND TEMPERING OF STEEL. 

hardened in a hurry, it will be more expeditious to 
place it upon a piece of cold sheet iron, and then to 
heat the iron and the saw in the midst of the ignited. 
fuel of a hollow lire ; and when it arrives at the 
proper temperature, it must be taken off the plate 
and immersed in the hardening fluid. By placing 
the saw upon a piece of cold, sheet iron, it causes 
the heat to be very slowly applied, and. it has a ten- 
dency to prevent the saw buckling in heating. Oil 
alone, or oil in which tallow has been dissolved, is 
sufficient to give the thinnest kinds of saws a suffi- 
cient degree of hardness ; but those of a medium 
thickness are the better for being hardened in solid 
tallow (the saws may be placed separately between 
two flat lumps of tallow). Tallow differs from oil in 
the absorption of heat for its fusion ; consequently, 
a more considerable degree of hardness is given to 
the steel by the tallow than by the oil ; besides, it 
hardens the steel to a greater depth than oil. Very 
thin blades of steel may be made sufficiently hard 
for some purposes by heating the blades to a red 
heat and then placing them between two heavy 
surface plates ; the surface plates will be better if 
they be smeared with tallow, previous to putting 
the blade between them. When the saws are re- 
moved from the hardening trough, they are general- 
ly brittle and warped ; consequently, they will re- 
quire to be tempered and hammered flat. The 
tempering may be performed in a variety of ways, 
depending of course upon the size, shape, and quan- 
tity. Circular saws, which are required for sawing 
hard substances (such as iron or steel), and which 



HARDENING AND TEMPERING OF STEEL. 159 

have a round spindle-hole, about one inch in diam- 
eter in them, will require to be tempered to a light 
straw color. These may be tempered by first bright- 
ening their surfaces, and then placing them upon a 
piece of hot iron. The piece of iron which will be 
required for tempering these kinds of saws may be 
made by the following method. Take a piece of 
round bar iron, one inch in diameter and eight or 
nine inches in length ; heat one end of it and ham- 
mer it so as to make it fit into the small square hole 
in the anvil ; at the opposite end of this piece of iron, 
and at about two inches from the extreme end, weld 
a moderate-sized iron collar ; the collar should be 
made of half round iron, so that it will, after it is 
welded upon the piece of round bar, form a large 
lump, the shape of a round ball. The object of 
this large lump is to retain the heat for a considera- 
ble time, so that several of the saws may be tem- 
pered before the iron will require to be reheated. 
If two of these lumps were made, one of them 
could be in the fire becoming heated, whilst the 
other lump is being used ; so that, if it were neces- 
sary, a continuance of the process may be kept up. 
The object of having this lump the shape of a round 
ball, is that it may not supply the heat too sudden- 
ly to the saw. If this lump was made flat, it would 
supply the heat too suddenly, unless it was used at 
a very low temperature ; it is evident it would not 
then temper more than one or two of the saws be- 
fore it would require to be reheated. The object of 
having this round lump welded upon a piece of 
round bar, i:^ for the convenience of keeping the 



160 HARDENING AND TEMPERING OF STEEL. 

lump in position upon the anvil, and to prevent the 
operator from always being in a stooping position 
when tempering the saws. The iron being finished, 
it is now ready to be heated for tempering the saws. 
The large lump will require to be heated to a reel 
heat, after which the opposite end of the iron must 
be placed in the hole in the anvil. The saws may 
now be placed (one at a time) upon the lump ; a 
slow rotary motion must be given to the saw, by the 
use of a small stick of wood, in order to equalize 
the heat. The end of the round bar at the top of 
the lump will help to supply heat and keep the saw 
in position whilst it is being turned round upon the 
lump. As soon as a light straw color appears upon 
the saw, it must be taken off the iron and cooled, 
either in water or oil ; or, if the heat has not been too 
suddenly applied, the saw may be allowed to cool in 
the air of its own accord. These kinds of small cir- 
cular saws are generally, after hardening, convex on 
one side and concave on the other. This imperfec- 
tion is owing to the outer part of the saw becoming 
too small to contain the central part. When the 
practice of securing the saws upon the spindle by 
circular plates screwed firmly against each side is 
adopted, a small degree of regular convexity is not 
very detrimental, because the plates bring the saw 
straight; but when they are convex in a greater de- 
gree, they will require to be slightly hammered. 
The outer part of the saw is the part which requires 
to be hammered, in order to expand the outer part 
and bring the middle flat. 

These kinds of saws may be tempered, and the 



HAEDENTNG- and tempering of steel. 161 

trouble of brightening their surfaces spared, by 
smearing them with oil or tallow and holding them 
one at a time over a slow clear fire until the oil or 
tallow begins to smoke, after which the saw must 
be immersed in oil and partly cooled; it must then 
be held over the fire a second time, until the oil 
again begins to smoke. If the saw is immersed in 
the oil and held over the fire a third time, it will 
ensure a more regular degree of temper. Care 
must be taken each time the saw is heated not to 
raise the temperature beyond that which is neces- 
sary to cause the oil to smoke ; otherwise the saw 
will become too soft for the purpose it is intended 
for — namely, cutting hard substances. By this 
method the saws acquire the same temper as that 
which they acquire when tempered to a straw 
color. A large quantity of these kinds of saws 
may be tempered more expeditiously by threading 
them upon a piece of iron wire, and then placing 
them in a proper vessel, with as much oil or tallow 
as will cover them (the wire is for convenience in 
lifting the saws out of the vessel), and then to place 
the whole over a small clear fire, or over a gas 
flame, until the oil or tallow begins to smoke, after 
which the saws must be taken out. They may then 
be cooled in water or oil, or they may be allowed 
to become cool in the air. This indicates the same 
temper as that called a straw color. 

Saw-blades which are required for sawing wood 
require to have the greatest amount ot elasticity 
given to them; consequently, after they are hard- 
ened, they will require to be tempered to the same 



162 HARDENING AND TEMPERING OF STEEL. 

temper as that called spring temper. This may be 
done by exposing the blade, the surface of which 
has been brightened, to the regulated heat of a 
plate of metal till the surface has acquired a blue 
color ; or it may be heated in a sand-bath heated to 
the proper temperature. To spare the trouble of 
brightening them, they may, like small circular 
saws, be smeared with oil or tallow and heated 
over a clear fire. It is obvious that the softer the 
steel is intended to be the more grease must be 
burnt off; consequently those saw-blades which 
are required for sawing wood, and which require 
to be sharpened with the file, will require to be 
heated till thick vapors are emitted and burn off 
with a blaze; two or three reheatings, and partly 
cooling them in oil when tempering, will, of course, 
insure a more uniform degree of temper. Saw- 
blades which are required for sawing wood, could, 
like those intended for sawing metals, be heated 
and tempered in hot oil; but, perhaps, it would 
not be very economical. The oil, of course, would 
require to be heated to a very high degree, in order 
to impart to the saws a spring temper ; so that it is 
questionable whether the time saved by this method 
would be sufficient to compensate for the waste of 
oil, which, at this high temperature, is considera- 
ble ; consequently, it becomes those who have such 
things to temper to adopt those methods which will 
answer their purpose the best. Saw-blades, unless 
hardened in a current of air, are generally, after 
hardening, buckled and twisted in various direc- 
tions ; this is caused by an unequal contraction of 



HARDENING AND TEMPERING OF STEEL. 163 

the blade, and it would be almost, if not quite, im- 
possible to prevent this unequal contraction, when 
it may arise from so many causes. The metal itself 
may be unequal in its texture. It may have been 
rolled at a temperature which was not uniform 
throughout the mass, or the blade may have been 
hammered more in one part than another ; this 
would be sufficient, from its unequal density, to 
cause unequal contraction ; or, if the temperature 
is not uniform tliroughout the blade when it is im- 
mersed in the hardening fluid, it will cause unequal 
contraction. 

Saw-blades which have become buckled and 
twisted in hardening, will, after they are tempered, 
require to be hammered flat; this operation re- 
quires a considerable amount of care and practice. 
It is obvious that the blades will require to be ham- 
mered at every part except those which are buckled. 
The hammering draws and expands those parts 
which are not buckled, and removes the unequal 
tension which has been caused by the unequal con- 
traction of the blade. The extent to which the 
blade will require to be hammered, of course, can 
only be ascertained by experience. 

"When saw-blades are well hammered, and the 
unequal tension has been removed, they are then 
fiat and more uniformly elastic ; but if the crust 
of the blade be partially or wholly removed by 
grinding, or in any other manner, the elasticity is 
proportionately impaired, and to restore the origi- 
nal excellence of this property, the blade will re- 
quire to be again hammered and afterward blued. 



164 HAKDEJSfING AOT) TEMPERING OF STEEL. 

Saws require to be made of the best cast steel, and, 
like all other kinds of tools, when required for cut- 
ting brass, require very sharp cutting edges ; they 
require also to be, in a slight degree, harder for 
brass and cast iron than for steel or wrought iron, 
otherwise they soon lose their sharp edges. 

When it is required to harden a single saw, such 
as is used for sawing off the ends of wood screws, 
or for sawing off the ends of small screw-bolts, or 
for occasionally sawing the grooves in the heads of 
screws, it may be heated to a cherry-red heat, and 
then placed flatways and horizontally between two 
lumps of tallow, or it may be pressed edgeways 
into a single lump of tallow. When it is intended 
to harden the saw by this last method, the saw 
should be slightly hammered at the back previous 
to heating and hardening it, otherwise the cutting 
edge will, in hardening, become convex, and the 
back edge will become concave. If the saw be- 
comes crooked sideways, it may be straightened by 
slightly hammering it with the pane of a small 
hammer at the concave side, at the same time press- 
ing with the fingers upon each end of the saw. 
The saw will be the better for being slio-htlv heated 
previous to hammering it ; it may be heated by 
placing the back side of it upon a piece of hot iron. 
If the saw should be found too hard for the purpose 
it is intended for, the back edge may then be placed 
upon the hot iron, and the saw tempered to a light 
straw color. 

When it is required to harden a lathe centre, it 
may be heated in an open fire ; the tapered part 



HAKDEJSTCNG AND TEMPERING OF STEEL. 165 

only requires to be heated, and this only to a low 
red heat ; the lowest heat that it will harden at is 
the most advantageous, as the centre is the more 
likely to keep true, and it will not afterward re- 
quire to be tempered. It must be immersed end- 
ways and perpendicularly in the water ; the back 
end of the centre must enter the water foremost ; 
it must be allowed to remain in the water until it 
becomes cool, after which it is ready for use. Lathe 
centres for large lathes, on account of the heavy 
weights they sometimes have to carry, ought always 
to be made of the most tenacious cast steel, which 
ought only to require a low red heat to harden. 

When it is required to harden a large or small 
quantity of fluted or other kinds of rimers, they 
may be heated in a similar manner to screw-taps, 
either by enclosing them in an iron box, and sur- 
rounding them on all sides with carbon, and placing 
the whole in a furnace or hollow fire, or by placing 
them in the midst of the ignited fuel of a small 
hollow fire. It will sometimes be more advan- 
tageous to heat these kinds of articles in red-hot 
lead, especially when a large quantity requires to 
be operated upon, because this is a very expeditious 
method for heating them, and they generally keep 
truer in heating by being surrounded on all sides 
with the uniform temperature of the lead, conse- 
quently they will keep truer in hardening. The 
lead, of course, must be heated to a certain tem- 
perature suitable to the steel. If the rimers are 
made of the best cast steel, the temperature of the 
lead need not be raised higher than what is neces- 



160 HARDENING AND TEMPERING OF STEEL. 

aary to heat the rimers to a cherry-red heat ; if the 
lead is too hot, it will burn the steel, and cause the 
rimers to be full of very small holes, which, of 
course, will unfit them for the purpose for which 
they are intended. If the lead by chance becomes 
too hot, it may be cooled down to the proper tem- 
perature by clipping a piece of cold iron into it. 

When it is intended to heat small rimers in red- 
hot lead, it will be necessary (previous to putting 
them into the lead), in order to protect them from 
the direct action of the heat, and to prevent the 
lead sticking to them, to brush them over with a 
little soft soap ; the largest and middle-size rimers 
will be the better for being brushed over with black- 
lead, mixed with water, or they may be brushed 
over with a mixture of lamp-black and linseed oil. 
If the black-lead and water is used, it will be well 
to dry the rimers previous to putting them into the 
lead, otherwise the dampness may cause the lead to 
fly and accidents may happen from it. Whichever 
method be adopted for applying the heat to rimers, 
they will require to be heated to a cherry-red heat, 
after which they must be immersed separately, end- 
ways, perpendicularly (except half-round rimers), 
and slowly in the water. Half-round rimers are 
very liable to become crooked, or concave on their 
round side, owing to the round side being the last 
to become cool ; consequently, they will require to 
be immersed in the same steady manner as the 
other kinds, but not so perpendicularly — they will 
require to have a more horizontal inclination. 
They may be immersed perpendicularly, provided 



HARDENING AND TEMPERING OF STEEL. 16 7 

they are slowly moved horizontally in the water in 
the direction of the round side, at the same time 
that they are being immersed endways, It must 
be borne in mind that red-hot lead will heat the 
steel much quicker than the ignited fuel of the fire ; 
consequently, when large fluted rimers are heated 
in lead, the cutting ribs of the rimers will arrive at 
the proper temperature much sooner than the cen- 
tral parts of the rimers, or before the innermost 
centre becomes at all heated ; and if the rimers 
are immersed in the water the moment the cutting 
ribs become sufficiently heated (and they may be 
immersed without fear of breaking them), the cen- 
tral parts of the rimers will remain soft; conse- 
quently, if large fluted rimers become crooked in 
hardening, they may be easily straightened. They 
may be straightened by laying them upon a block 
of hard wood, or upon a block of lead, and then 
putting a piece of round iron (the size of the groove) 
into the groove at the convex side, and then strik- 
ins: the iron with the hammer. If the rimers be 
tempered previous to striking them with the ham- 
mer, they will straighten the easier. When small 
fluted rimers are heated in red-hot lead, they be- 
come heated through almost instantly they are put 
into the lead ; consequently, it must be obvious that 
if these become crooked in hardening they cannot 
be straightened in the same manner as the larger 
sizes ; therefore, in order to guard against their be- 
coming crooked, they must be allowed to remain in 
the heated lead until they become uniformly heated 
to their innermost centre, and then immerse them 



168 HARDENING AND TEMPERING OF STEEL. 

endways and perpendicularly and very slowly in the 
water, and entirely quench them ; and if any of 
them become crooked, it will be well to soften them 
again, then straighten and reharden them. Care 
must of course be taken not to raise the temperature 
of the lead higher than what is necessary to heat 
the rimers to the proper temperature suitable for 
hardening them. The method I have myself some- 
times adopted when hardening fluted rimers is this. 
I have heated them separately in red-hot lead, and 
then immersed them separately, endways and per- 
pendicularly, in the water, having the water of a 
suitable depth, so that when a rimer was immersed 
and the extreme end of it made to touch the bottom 
of the tank and then withdrawn, it would harden 
the cutting edges of the rimer and leave sufficient 
heat in the central part, so that the rimer would, if 
it were crooked, admit of being straightened, either 
by placing it between the centres of a turning lathe, 
and striking it upon the convex side with a small 
wooden mallet, or by placing it upon a block of 
hard wood, or a block of lead, and striking upon 
the convex side with the mallet. As this method 
requires a great amount of experience and dexterity, 
and as there is great risk of the rimers breaking 
when they are struck with the mallet, especially if 
they be allowed to become too cool previous to strik- 
ing, it will be well, perhaps, for the operator (in 
order to avoid any considerable obstacle) to adopt 
the method previously explained, that of immersing 
them endways, perpendicularly, and slowly in the 
water, and entirely quenching them. 



HARDENING AND TEMPERING OF STEEL. 169 

Bimers after they are hardened will require to 
be tempered, which may be done by adopting sim- 
ilar methods to those to be adopted for tempering 
screw-taps. Fluted rimers will require to be ten> 
pered to a yellowish- white, or light straw color; six 
and eight sided rimers will also require to be tem- 
pered to a light straw color ; square, and triangular, 
and half-round rimers will require to be tempered 
to a dark straw color. The reason why square, and 
triangular, and half-round rimers require to be re- 
duced lower in temper than the other kinds is, that 
they take hold of the work so deeply that they are 
very liable to break by the force requisite to 'turn 
them round. Six and eight-sided, and square and 
half-round rimers, which have become slightly 
crooked in hardening, may be straightened by 
screwing a chipping hammer (flat face uppermost) 
between the jaws of a pair of vice ; the convex side 
of the rimer may then be laid upon the hammer 
face, whilst the concave side is slightly hammered 
with the sharp pane of a small hammer, at the same 
time pressing with the fingers upon each end of the 
rimer. If the rimers (previous to hammering) be 
slightly heated, they will straighten the easier, and 
be less liable to break. 

Small drills, gouge-bits, centre-bite, counter- 
sinks, gimblets, bradawls, or sprig-bits, etc., may 
be expeditiously hardened by dipping their cutting 
parts into red-hot lead, and then cooling them in 
water. When it is intended to dip several of any 
of these kinds of articles at once into red-hot lead, 
it will be necessary to have a pair of tongs with 



8 



170 HARDENING AND TEMPERING OF STEEL. 

long jaws for gripping the articles. One of the 
jaws of the tongs will require to be made hollow 
inside, and the other jaw made flat ; the hollow 
jaw is for convenience — for binding a piece of wood 
into it — so that if the articles should happen to be 
of an unequal thickness the tongs may grip them 
all, as the most prominent parts of them will sink 
into the wood. When the wood becomes too much 
worn, it may be replaced with another piece. Any 
quantity of these articles may be heated as expedi- 
tiously as a single article, if there be sufficient lead. 
Gouge-bits, gimblets, bradawls, or sprig-bits, will 
require to be tempered after they are hardened. 
They may be tempered by placing them upon a 
piece of hot iron and heating them until a blue 
color appears upon their surfaces, and then pushing 
them off the hot iron into a vessel containing cold 
oil ; or, if the heat has not been too suddenly applied, 
they may be allowed to become cool in the air of 
their own accord. A large quantity may be tem- 
pered at once by placing them in a proper vessel 
with as much oil or tallow as will cover them, and 
then placing the whole over a small fire and slowly 
heat the oil until it will take fire if a light be pre- 
sented to it, but not so hot as to burn when the 
light is withdrawn. The articles may then be 
lifted out of the oil (that is, providing the vessel is 
furnished with a false bottom), or the whole may 
be tipped out of the vessel upon a thin sheet of iron 
which is slightly curved and placed in a slanting 
position, with a vessel placed at the bottom to catch 
the oil ; the articles may then be allowed to drain 



HARDENING- AND TEMPERING OF STEEL. 171 

and become cool of their own accord, tliev will 
then be the same temper as if their surfaces were 
blued upon hot iron. 

Centre-bits and countersinks for cuttinc; wood 
require to be tempered to a purple color. The 
heat may be applied to these either by a piece of 
flat bar iron or by an iron ring heated to redness, 
or they may be placed in a proper vessel contain- 
ing oil or tallow, and then placed over a small fire 
and the whole slowly heated until the oil yields a 
thick black smoke, but not so hot as to take fire 
if a light be presented to it. The articles must then 
be taken out of the oil and allowed to become cool ; 
they will then be the same temper as if their sur- 
faces were changed to a purple color upon hot iron. 

Red-hot lead is an excellent thing in which to 
heat any long plate of steel that requires hardening 
only on one edge, for it need not be heated in any 
other part but that which is required hard, and it 
will then keep straight in hardening ; at least, it 
will keep very much truer than if it were heated 
in the midst of the ignited fuel of the fire. 

If a long steel plate which requires to be hard- 
ened only on one edge, be heated in a furnace or in 
the midst of the ignited fuel of a hollow or open 
fire, and then the whole body of it immersed in the 
water, it will become very much twisted and warped, 
and will cause a deal of trouble to set it straight 
again, even though the steel be tempered previous 
to being hammered, especially to those who are un- 
acquainted with the way of hammering and setting 
steel plates in a hardened state. If the plate be 



172 HARDENING AND TEMPERING OF STEEL. 

heated throughout its body, and if only one edge 
of it (the edge which is required hard) be im- 
mersed in the water, or, in other words, if the plate 
be only partially immersed, the plate will become, 
in a great degree, concave on one edge and convex 
on the other. The edge of the plate which goes 
in the water becomes convex, and the edge which 
does not enter the water becomes concave. This is 
owing to that part of the plate which is below the 
surface or the water contracting and becoming 
shorter by the loss of heat, and compressing the 
red-hot part of the plate which is above the surface 
of the water into a denser state ; moreover, after 
that part of the plate which was below the surface 
of the water has become quite cool, it will be in a 
slight degree longer than what it was when in its 
soft state, consequently this has a tendency to push 
the red-hot part of the plate round, and thereby 
helping to cause the uppermost edge of the plate to 
become concave. 

After the whole body of the plate has become 
cool, the hardened part, as well as the soft part of 
the plate, will sometimes be shorter than what it 
was previous to hardening, even though the hard- 
ened part did expand longer in hardening. This 
is caused by the soft part of the plate contract- 
ing by the loss of heat after the hardened part has 
become cool, and thereby compressing the hard- 
ened part into a denser state. If red-hot lead is 
used as a source of heat, and the edge of the plate 
only (which is required hard) be put into the lead, 
it is obvious that the other part of the plate will 



HARDENING AND TEMPERING OF STEEL. 173 

remain cool ; consequently, when the plate is en- 
tirely immersed in water, the hot part of the plate 
will not act with sufficient force to alter the cool 
j>art, consequently the cool part of the plate tends 
to keep the hardened part true. It may be inquired, 
if the part which goes in the lead expands longer 
in hardening, and is not able to act with sufficient 
force to compress the cool part, will not the hard- 
ened part become twisted and buckled ? The an- 
swer to this is : it will not become twisted or buckled 
by the expansion (though it may become crooked 
in a slight degree by the unequal hammering, or 
the unequal density of the steel), because the heated 
. part of the plate has been compressed by the cool 
part during the time it was expanded by the heat, 
consequently the expansion will generally be about 
equal to the compression, and the plate will be 
about the same dimensions that it was previous to 
hardening. 

Should the hardened part of the plate happen 
to become in a slight degree longer than what it 
was previous to hardening, it is a proof that the 
expansion predominates over the compression ; if, on 
the contrary, it becomes shorter, it is a proof that 
the compression predominates over the expansion. 

When it is intended to heat articles in red-hot 
lead, they ought not to be plunged too quickly into 
the lead : plunging cold steel too suddenly into red- 
hot lead has a tendency to cause it to become 
crooked in a similar manner as red-hot steel be- 
comes crooked when it is plunged too suddenly into 
cold water. 



ITi HARDENING AND TEMPERING OF STEEL. 

All articles which are heated in red-hot lead 
should be slightly moved up and down in the lead 
during the time they are becoming heated, other- 
wise the heat will be apt to terminate in a strict 
line, and will probably cause them to crack when 
they are immersed in the water. 

A very good vessel in which to heat the lead 
when one edge of a long plate is required to be 
heated, is made by taking a piece of three-inch 
angle iron, a few inches longer than the plate to be 
hardened, and slitting and turning, and welding 
each end of the angle iron so as to form a kind of 
trough. A long fire will be required for heating 
the angle iron and the lead. A fire of any length 
may be made by taking a piece of wrought iron 
pipe, and boring some holes into it in the direction 
of its length. The holes will require to be about 
five-eighths of an inch in diameter, and about three 
inches apart; one end of the pipe must then be 
inserted into the aperture of the tuyere. A row 
of bricks must be placed on each side of the pipe, 
at a suitable distance from it, so as to leave room 
for the fuel and the angle iron between the bricks. 
The pipe will require to be covered over with loam 
or fire-clay, in order to keep it from burning ; pre- 
vious to covering the pipe over, each hole should 
be stopped with a piece of wood, so that the loam 
may not get into the pipe, or stop up the holes in 
the pipe ; after the covering up of the pipe is com- 
pleted, the pieces of wood may then be pulled out 
of the holes, and the fire lighted. The fire will 
burn with more regularity if the first three or four 



HARDENING AND TEMPERING OF STEEL. 175 

holes (at that end of the pipe which enters the 
tuyere) be a little larger than the others, as the 
blast is always strongest at the far end of the pipe. 
A loose plug will, of course, be required for the far 
end of the pipe to stop the blast ; and if at any 
time the pipe becomes stopped by the ashes falling 
through the holes of the pipe, the loose plug may 
be taken out, and the ashes blown out of the pipe ; 
the plug may then be put back into its place. If 
more durable things than the angle-iron and pipe 
be required, a loDg fire-tile may be chipped out to 
the proper shape, and made to answer the purpose, 
and a small special furnace constructed for heating- 
it. A pot for melting a small quantity of lead may 
be made by welding a plug into one end of a piece 
of wrought iron pipe ; but this is not very durable, 
as the high temperature of the lead will soon cause 
it to burn into holes, and allow the lead to run out 
into the tire. 

When a more durable thing than the wrought 
iron pipe is required, and a larger quantity of lead 
requires heating, a crucible similar to those used in 
brass foundories will be suitable. Crucibles contain- 
ing a large quantity of lead cannot conveniently be 
heated in a common smith's fire ; consequently, a 
suitable furnace must be constructed for the pur- 
pose. When it is necessary to heat the lead in a 
crucible, it should be made red-hot previous to put- 
ting the lead into it ; and, in heating the crucible, 
the same plan must be adopted as that which is 
generally adopted in brass founderies ; namely, put- 
ting; the crucible in the fire with its mouth down- 



176 HARDENING AND TEMPERING OF STEEL. 

ward, in order that the heat may act upon the in- 
side and the outside of the crucible at the same 
time, and so cause a more uniform expansion of the 
crucible, and lessen the risk of its cracking. The 
crucible need not be reversed until it has become 
red-hot ; then it will be ready to receive the lead. 
If the crucible be put in the hre' bottom down- 
ward, the heat for a time would only act upon the 
outside, consequently it would cause an unequal ex- 
pansion, and increase the risk of its cracking. 

Another thing to be observed is, that the sur- 
face of lead when melted in open vessels becomes 
quickly covered with a skin, or pellicle. This is 
occasioned by the action of the oxygen of the at- 
mosphere, the activity of which soon causes the skin 
to increase in thickness, and wastes the lead so fast 
that it becomes an object of importance to those 
who use much lead to check its formation, or con- 
vert it when formed into the metallic state aojain. 
Charcoal, or fatty substances, assisted by sufficient 
heat, convert this dross, or oxide, into metal again ; 
but if a covering of charcoal or cinders be kept on 
the surface of the melted lead, the oxide will not 
form. When it is allowed to form, it not only 
wastes the lead, but is a great obstruction to get- 
ting the articles in and out of the lead. 

In a former part of this work it has been recom- 
mended to allow steel when heating for hardening 
(in order to assist the process) ample time to soak 
and become uniformly heated to its innermost centre. 
In this place (on the subject of heating steel in red- 
hot lead) it is stated that large fluted rimers may 



HARDENING- AND TEMPERING OF STEEL. 177 

be immersed in the water without fear of breaking 
them immediately their cutting ribs or edges become 
uniformly heated to the proper temperature suitable 
for hardening them, without waiting for the central 
steel to become heated. As this will probably be 
noticed by some persons who may not perhaps give 
it sufficient thought to ascertain the true meaning 
of it, it will then appear to them that one part of 
the work is in contradiction to the other part ; con- 
sequently, I have thought it necessary in this place 
to give an explanation to it so as to prevent the 
reader misunderstanding it. In the first place, it 
will be necessary to repeat that red-hot lead will 
heat steel much quicker than the ignited fuel of the 
fire ; consequently, when such an article as a large 
fluted rimer is dipped into the red-hot lead, the sur- 
face steel will become uniformly heated before the 
central steel has acquired sufficient heat to cause it 
to expand (at least, from the short time the rimer is 
in the lead the central steel can only become expand- 
ed in a very small degree) ; consequently, when the 
rimer is immersed in the water, the surface steel in 
cooling has not to compress the central steel, neither 
has the central steel to contract after the outer crust 
is fixed ; consequently, a large fluted rimer may be 
immersed into the water (without risk of breaking- 
it) immediately the cutting ribs arrive at the proper 
temperature suitable for hardening them. If the 
surface steel of any article, when placed in a hollow 
or open fire, could be uniformly heated without 
heating or expanding the central steel, there would 
be no necessity for allowing the steel to soak or be- 
8* 



178 HARDENING AND TEMPERING OF STEEL. 

come uniformly heated to its innermost centre ; but 
as the surface steel cannot, in a hollow or open fire, 
be uniformly heated without causing the central 
steel to become heated and expanded also, it be- 
comes then quite necessary to heat the central steel 
to the same temperature as the surface steel, in 
order that the central steel may admit of being 
compressed by the surface steel when it is immersed 
in the water. "When the central steel of any article 
becomes heated and expanded, and not sufficiently 
softened to admit of being compressed by the sur- 
face steel (when becoming cool), it will have a tend- 
ency to hold the surface steel in such a state of 
tension that it will sometimes cause it to crack in 
several places, and the surface steel will sometimes 
shell off in flakes ; consequently, it must be seen 
that if the central steel is heated at all, it is requisite 
to heat it uniformly with the surface steel ; it will 
then lessen the risk of its breaking in hardening. 
For further information upon this subject, I must 
refer the reader to the chapter upon the expansion 
and contraction of steel. 

"When it is required to harden large or small 
drifts in large or small quantities, they may be 
heated in a similar manner as screw-taps, either by 
enclosing them in an iron box and surrounding 
them on all sides with carbon, and placing the 
whole in a furnace or hollow fire, or by placing 
them in the midst of the ignited fuel of a hollow 
fire. Whichever method be adopted, they will re- 
quire to be uniformly heated to a cherry-red heat. 
When they arrive at the proper heat, they will re- 



HARDENING AND TEMPERING- OF STEEL. 179 

quire to be immersed separately, endways, perpen- 
dicularly, and slowly in the water ana entirely 
quenched. After the drifts have become quite cool 
and been taken out of the water, they will require 
to be brightened and tempered ; they may be tem- 
pered by adopting similar methods to those which 
are to be adopted for tempering screw-taps. Drifts 
will require to be tempered to a brown color. 

When it is required to harden a quantity of 
large common drills, and which have been allowed 
to become quite cool after having been forged, they 
may be placed, several at once, or as many as con- 
venient, in the midst of the ignited fuel of a very 
small hollow fire, or they may be heated in an open 
fire, taking care to keep their points out of the 
hottest part of the fire at first, and gradually draw- 
ing their points toward the hotter part of the fire 
as the upper parts become heated. A considerable 
portion of the drill will require to be heated to a 
cherry-red heat. The blast, of course, must be 
sparingly used. When the drills arrive at the prop- 
er heat, they must be taken out of the fire sepa- 
rately. Those in advance of the others must be the 
first to be taken out ; a part of the heated portion 
of the drill must then be immersed in the water. 
It must not be forgotten that it is requisite to put 
the water in motion previous to clipping the point 
of the drill into the water, or otherwise, to give the 
drill a vertical, or other movement, immediately it 
arrives to the proper depth in the water. That part 
of the drill which is below the surface of the water 
must be allowed to remain in until it becomes quite 



180 HARDENING AND TEMPERING OF STEEL. 

cool, after which it must be taken out, and the cut- 
ting part brightened, which may be done by rubbing 
the surface with a piece of grindstone, or with an 
emery stick, or with a piece of emery cloth. The 
drill may then be laid upon the anvil, or any other 
suitable place, whilst another is drawn out of the fire 
and treated in a similar manner. The heated portion 
of the drills which were not immersed in the water 
will then continue to supply the heat to temper the 
cutting parts of the drills. After the second drill 
has been immersed, it may be placed alongside 
the first drill, and another drill withdrawn from the 
fire, and so on, until all that have been heated have 
been immersed. The hardener must of course 
(during the time he is drawing the drills out of the 
fire and dipping them into the water) have his atten- 
tion upon those he has placed upon the anvil, so that 
he may see when the cutting parts arrive at the proper 
temper ; as soon as a uniform dark straw color ap- 
pears upon the cutting parts of the drills, they must 
be instantly cooled in the usual manner, otherwise 
the upper part of the drills may continue to supply 
heat, and the cutting parts will become too soft 
Should it happen that the heat at the back part of 
any of the drills is insufficient to temper the cutting 
part, it will be advisable, in order to complete the 
tempering, to hold the drill for a few moments in a 
gas flame, if the gas is lighted ; or it may be placed 
upon a piece of hot iron, if there is a piece of hot 
iron ready at hand ; or a few hot ashes may be 
drawn out of the centre of the fire, and the drill 
held over them. All drills which are intended to 



HARDENING- AND TEMPERING- OF STEEL. 181 

bore holes less than the quarter of an inch (and 
when a quantity are required to be hardened) must 
not, like the larger kinds, be heated and partially 
immersed ; but their cutting parts only should be 
heated to a cherry-red heat, and the drills wholly 
immersed and entirely quenched. They may subse- 
quently be tempered by first brightening their cut- 
ting parts, and then placing them several at once 
upon a piece of bar iron heated to redness. Their 
cutting parts must be allowed to project some dis- 
tance over the heated iron, otherwise the heat will 
be too suddenly applied. As soon as a dark straw 
color appears upon their cutting parts, they must 
be cooled in the usual manner. 

Miniature drills, such as those used by clock- 
makers and others, cannot conveniently be heated 
in the midst of the ignited fuel of the fire ; though 
some of them may be heated in charcoal dust, heated 
to a red heat. These small drills are generally 
heated in a gas flame, or in the name of a candle ; 
they are hardened by plunging suddenly their 
heated points into a lump of tallow or into the grease 
of the candle. They are tempered, if found too hard, 
by taking a little of the tallow upon their points, 
and then placing them in the flame at a short dis- 
tance above the point, and holding them there un- 
til the tallow upon the point begins to smoke ; the 
cutting part of the drill is then of the same temper 
as if it were brightened and tempered to a straw 
color. By any of the methods just explained, the 
cutting parts of drills are tempered to a straw color, 
while the rest is not higher than blue, so that the 



182 HARDENING AND TEMPERING OF STEEL. 

liability of their breaking when in use is greatly 
diminished. 

It has previously been stated that chipping- 
chisels will be the better if the hammering (when 
forging them) be continued until the cutting part 
becomes nearly cool ; and, perhaps, it will not be 
amiss to state here that it is better to harden and 
temper them after being forged, and while the part 
above the cutting edge is in a red-hot state, than to 
allow them to become quite cool, and then to re- 
heat them for hardening. The reason for this is, 
greater care is required to heat them properly after 
they have become quite cool ; consequently, there 
is greater risk of the effect of the hammering be- 

CD 

ing taken off again. 

When a large quantity of chipping-chisels have 
been forged, and have been allowed to become quite 
cool, and which may require to be hardened and 
tempered, similar methods must then be adopted, 
as those which are to be adopted for hardening and 
tempering the largest kinds of common drills, with 
the exception that the chisels will require to be 
tempered to a violet color, that is, if they are re- 
quired for chipping metals. If the chisels are re- 
quired for chipping stone, they will require to be 
tempered to a purple color. The force required for 
chipping stone being less than for metals, it is 
obvious that the chisels are less liable to break ; 
consequently (in order to prevent them wearing 
away so fast) they may with safety be left in a 
slight degree harder. 

When it is required to harden those kinds of 



HARDENING AND TEMPERING OF STEEL. 183 

small chipping-chisels, which are used for chipping 
the delicate kinds of work, they must not, like the 
larger kinds, be heated and partly immersed, but 
their cutting part only should be heated to a cherry- 
red heat. They should then be wholly immersed 
and entirely quenched. They may subsequently be 
tempered by first brightening their cutting part, 
and then placing them, several at once, upon a 
piece of bar iron heated to redness. As soon as 
their cutting part becomes changed to a violet 
color, they must be instantly cooled in the usual 
manner. 

When a common turning-tool is required extra- 
ordinarily hard for cutting very hard cast iron, it 
will be necessary, in the first place, to heat the tool 
to a red heat, and then give it a judicious hammer- 
ing until it becomes, nearly cool, after which it will 
be necessary to heat some lead to a bright red heat ; 
a small quantity of charcoal dust must be placed 
upon the surface of the heated lead to prevent oxi- 
dation. During; the time the lead is becoming; 
heated, the cutting part of the tool should be heated 
to a low red-heat in an open fire. After the lead 
has become heated to a bright red heat, and the 
cutting part of the tool to a low red heat, the tool 
must then be drawn out of the fire, and while it is 
at a red heat the scale must be removed with the 
file ; the cutting part of the tool must then, as soon 
after filing as possible, be put into the heated lead. 
It must be allowed to remain in the lead until it 
becomes heated to the same temperature as the lead 
— a bright red heat; after which it must be taken 



184 HARDENING AND TEMPERING OF STEEL. 

out of the lead and instantly plunged into a bucket 
of pure cold water, and a rapid movement given to 
it, and entirely quenched ; after which, when taken 
out of the water and ground upon the grinding- 
stone, it is ready for use. By this method the steel 
acquires a greater degree of hardness than will be 
readily imagined by those who have never tried it. 

When it is required to harden small spiral 
springs which are made of steel wire, or springs 
for locks, or any of the other kinds of slight springs, 
they will require to be uniformly heated to a cherry- 
red heat, and then immersed in cold oil (not oil 
which has been long in use and become thick), and 
entirely quenched. Springs of a medium thickness 
will be the better for being cooled in water, the 
water being previously heated to about 60 degrees 
of heat, and the surface of which should be covered 
with a film of oil. The thickest kinds of springs 
will be the better for being cooled in pure water 
heated to about 70 degrees of heat. Springs require 
to have the greatest amount of elasticity given to 
them ; consequently, they will, after they are hard- 
ened, require to be tempered. They may be tern- 
pered separately by smearing them over with oil or 
tallow and then holding them over a clear fire, or 
in a hollow fire, or in the inside of a piece of large 
iron pipe inserted in the midst of the ignited fuel 
of an open fire, and uniformly heating them until a 
white flame burns upon them, or, in other words, 
until the grease burns off with a blaze. If it is a 
spiral spring (or any other kind of spring which is 
not thicker at the ends than at the central part) 



HARDENING- AND TEMPERING OF STEEL. 185 

which is being tempered, and which is shorter in its 
length than the length of the fire, it will be very 
apt to become heated at the extreme ends first ; con- 
sequently, as soon as the two ends arrive at the 
proper temperature (which is known by the grease 
taking fire) the spring must be immersed in oil : it 
must not be entirely quenched, but must be taken 
out of the oil again immediately, and then again 
exposed to heat. If the oil upon the ends takes fire 
again sooner than the oil upon the middle part of 
the spring, it must then be immersed again in oil, 
and then again exposed to heat, and so on until the 
oil burns uniformly upon all parts ; otherwise -the 
spring cannot acquire a uniform temper. After 
the spring has become uniformly heated to the 
proper temperature, and the oil burns uniformly 
upon it, it must then be again immersed in oil, then 
taken out again immediately and allowed to become 
cool in the air of its own accord. It will then be 
fit for use. All kinds of springs, whatever their 
shape or whatever their size, may be tempered per- 
fectly by this method. It must be borne in mind 
that there is but one certain temper which gives to 
steel its greatest amount of elasticity ; consequently, 
the stiffness or pliability of springs must be regu- 
lated by the substance and shape of the steel from 
which they are made. A very convenient way of 
tempering a large quantity of small springs at once 
(they must, of course, be previously hardened), and 
of heating them uniformly, no matter how irregular 
their shape, provided the heat is not too suddenly 
applied, is to bind a quantity of them together with 



186 HARDENING AND TEMPERING OF STEEL. 

a piece of iron binding-wire and then to put them 
into a suitable vessel with as much oil or tallow as 
will cover them. Then place them over a small 
clear fire, and slowly heat the whole. Just as the 
oil begins to boil the springs must be lifted out, 
when a white flame will burn uniformly upon the 
whole of them; they must then be immersed into 
cold oil, — they need not be entirely quenched, but 
they may be taken out of the oil again immediate- 
ly and allowed to become cool in the air of their 
own accord, and when cool, they will be like those 
which have been blazed off separately over the fire, 
and- fit for use. A separate spring may be attached 
to a separate piece of wire, which may be lifted out 
of the oil occasionally, to ascertain when the whole 
is at a proper heat, which is known by the white 
color of the flame upon the spring. 

Large springs may be tempered by this method, 
but the time saved with large springs will not be 
sufficient to compensate for the waste of oil ; conse- 
quently, it will be more economical to temper the 
largest springs by blazing over the fire. 

It would be well for those who are not accus- 
tomed to the operation, before attempting to boil a 
large quantity of springs, to boil a single one in a 
small quantity of oil, and so make themselves ac- 
quainted with the proper temperature of the oil, 
and the proper temper of the spring. 

I will now bring this chapter to a conclusion, 
not because I have no more to say, but because I 
do not think it necessary to say more ; but I may 
add, that the hardness of cutting tools and the an- 



HARDENING AND TEMPERING- OF STEEL. 187 

gles forming their edges, must be varied according 
to the strength and hardness of the material to he 
worked. The harder materials require tools with, 
more obtuse-angled edges, and no cutting-tool will 
act upon a substance harder than itself. 

The number of turns which the mandrel of the 
lathe ought to make in a given time must also be 
varied according to the strength and hardness of 
the material to be worked. The velocity of rotation 
for wood can scarcely be too swift, it must be 
rather slow for lead, brass, copper, gun-metal, and 
bell-metal ; still slower for ordinary cast iron, forged 
iron, and steel, and slowest of all for tempered steel, 
and chilled cast iron ; or, in other words, for cast 
iron which has been cast in iron moulds, or other 
good conductors of heat. 

The reason for these limits is, that a certain 
amount of time, varying with the material, is re- 
quisite for the act of cutting to take place, and that 
the tools, if much heated, will instantly become soft 
and cease to cut. 



CHAPTER TIL 

EXPANSION" AND CONTRACTION OF STEEL. 

Expansion and contraction belonging- to tins 
subject is the enlargement, or increase, or decrease, 
in the bulk of the steel, as the case may be, in con- 
sequence of a change in the particles by the process 
of hardening. It is pretty generally known to those 
who are employed at the process of hardening steel, 
and to those in the habit of fitting up various kinds 
of work requiring great nicety, that the hardening 
of steel often increases its dimensions ; so that such 
pieces of work, fitted with nicety in their soft state, 
will not fit when hardened, and the workman has 
therefore to resort to the process of grinding or lap- 
ping to make the work fit. 

The amount of the expansion (or the amount of 
the contraction of steel) cannot be exactly stated, as 
it varies according to the size of the steel operated 
upon, and the depth to which the steel hardens ; also 
in the different kinds according to the amount of car- 
bon combined, and even in the same steel operated 
upon at different degrees of heat. Steel which is the 
most liable to injury by excess of heat is the most 
liable to these expansions ; and steel which is less lia- 
ble to injury by heat is the most liable to contrac- 
tions. As, for example, the more carbon the steel 



EXPANSION AND CONTRACTION OF STEEL. 189 

contains, the greater will be the expansion of the 
steel ; and the nearer the steel approaches to the state 
of iron, the less will be this increase of bulk. 

Although steel expands in hardening, it is not 
universal for pieces of all sizes to increase in dimen- 
sions ; for sometimes it is smaller in dimensions after 
hardening. This, at first sight, appears anomalous ; 
but I will endeavor to give an explanation of it. 

Steel, like all other substances composed of par- 
ticles, varies in its dimensions with a change in 
temperature. It follows that when the steel is at a 
red heat, the natural positions of its particles are in 
a measure displaced, and it is expanded to a great- 
er bulk ; and when immersed in water and suddenly 
cooled, such a change of its particles takes place as 
to make it hard and brittle. It also contracts to a 
smaller bulk by the loss of heat ; but this cannot so 
rapidly occur at the central part, because it is pro- 
tected by the surface steel. Consequently, large 
pieces of steel do not harden all through ; or, in 
other words, do not harden properly to their centres, 
bnt toward the centre the parts are gradually less 
hard, and will sometimes admit of being readily 
filed ; and as it is only the outer parts of the steel 
which harden properly, consequently it is only those 
parts of the steel which harden that increase in 
bulk. When the steel is immersed in the water, the 
water begins first of all to act upon the outer crust 
of the steel, and then cooling it gradually toward 
the centre. The outer crust being the first to part 
with its heat, it is of course the first to contract and 
become smaller. The outer crust in contracting is 



190 EXPANSION AND CONTRACTION OF STEEL. 

held in a state of great tension, by having to com- 
press the central steel (the central steel at the time 
being expanded by the heat). "While the surface 
steel is in this state of tension, and the central steel 
in this state of compression, the particles of the sur- 
face steel (by the strain) are displaced at a greater 
distance from each other, and the particles of the 
central steel (by the compression) are compressed 
into a denser state. The particles of the central 
steel being compressed into a denser state, it causes 
the central steel, after it has become quite cool, to 
occupy less space than what it did previous to hard- 
ening. The particles of the surface steel become 
hard while in this state of tension, consequently the 
hardened part of the steel becomes fixed, and can- 
not return to its original bulk : consequently, the 
hardened part of the steel occupies more space than 
what it did previous to hardening. 

If the displacement of the particles of the outer 
steel predominates over the compression of the par- 
ticles of the central steel, the piece of steel under op- 
eration will then be larger in dimensions. If the 
compression of the particles of the central steel pre- 
dominates over the displacement of the particles of 
the outer steel, the piece of steel under operation 
will then be smaller in dimensions. In other words, 
if the expansion of the outer steel amounts to more 
than the compression of the central steel, the piece 
of steel will increase in bulk ; if the compression 
of the central steel amounts to more than the expan- 
sion of the outer steel, the piece of steel will then 
decrease in bulk. The expansion of the steel is 



EXPANSION AND CONTRACTION OF STEEL. 191 

greatest when it is heated to a high degree of heat 
before immersion. This effect is owing to the par- 
ticles being displaced at a still greater distance from 
each other, and which may, in some measure, ac- 
count for the brittleness of steel when overheated. 
This expansion is, in some measure, reduced in tem- 
pering; and this effect is caused by the hardness 
being reduced and allowing the particles to partly 
rearrange themselves to then* natural positions. 

It is believed by some, that the hardness of steel 
is caused by the compression of the whole of the par- 
ticles into a denser state ; in confirmation of this, 
they say that steel after hardening always looks closer 
and finer in the grain. Now, if this were the only 
cause of steel becoming hard, how does the steel get 
larger in dimensions ? Pieces of steel of all sizes 
would, according to this, universally become smaller. 
The compression of the particles of the central steel 
into a denser state certainly does take place, as I 
have before remarked ; but the particles of the out- 
er parts of the steel are displaced at a greater dis- 
tance from each other, or the steel could not be- 
come larger in dimensions. It is believed by some, 
that if a piece of steel (in hardening) increases in 
bulk in one part, that it must decrease in bulk 
in proportion in another part. Now, if this were 
the case, how is it that the specific gravity 
of some pieces of steel is reduced by hardening ; 
and how is it that workmen have often to grind or 
lap pieces of steel to make them fit the same places 
which they fitted previous to hardening ? It may 
be said that the steel may be prevented from fitting 



192 EXPANSION AND CONTRACTION OF STEEL. 

the place it previously fitted by becoming crooked 
or oval in hardening ; but, if this were the only 
cause, how could it be made to fit its place again by 
grinding or lapping ? It would be impossible (un- 
less it were softened and upset) to make the lean or 
concave side of it fit its place again. I may also 
inquire, what is the cause of steel being whiter in 
color after hardening? As I have previously re- 
marked that it is only those parts of the steel which 
harden properly that increase in bulk, it may per- 
haps be asked, how is it that a piece of bar steel 
becomes shorter in hardening ? The answer is, that 
the central steel is compressed by the surface steel 
endways as well as sideways, by the surface steel 
contracting shorter by the loss of heat. The cen- 
tral steel contracts after the outer crust is fixed, con- 
sequently an internal strain is caused ; and, if the 
steel becomes shorter than what it was previous to 
hardening, it is because the force of this internal 
strain shortens the outer steel more than it expands 
in hardening. 

It is quite reasonable to suppose, if the particles 
of the hardened parts of the steel are removed to a 
greater distance from each other, that the steel 
would look considerably more open and coarser in 
the grain ; consequently, it may be inquired, if it is 
not "the compression of the whole of the particles 
into a denser state, what is the cause of steel look- 
ing closer in its texture after hardening? The 
answer is, if we accept the theory that it is the 
crystallization of the carbon which causes the hard- 
ness in steel, that the carbon expands in the act of 



EXPANSION AND CONTK ACTION OF STEEL. 19 



o 



crystallization (in a similar manner that water ex- 
pands by extreme cold in crystallizing into ice) and 
fills np every pore or crevice, and gives the steel 
the appearance of being closer and more solid. 

Such is a slight sketch of the expansion and con- 
traction of steel ; and, although much more might be 
said, I have not thought it necessary to entangle 
the feacler with a lot of theories, although it may be 
necessary for his amusement, and for the exercise 
of sound, judgment, to occasionally glance at them 
in treating fully the purely mechanical operations. 

The expansion of steel is prevented in some 
measure by annealing the steel about three times 
previous to its being finished, turned, or planed ; 
for instance, after the first skin is cut from the steel 
it should, be annealed, again, after which another 
cut must be taken from it and. again annealed, and 
so the third time. This may appear to some like 
frittering away time; but in many instances the 
time will be more than saved in lapping or grind- 
ing to their proper sizes after the articles are hard- 
ened, especially when it becomes necessary to lap or 
grind them by hand-labor, for hardened, steel works 
with great difficulty ; therefore in some instances it 
becomes a matter of importance in hardening to keep 
the article as near as possible to its original size. I 
have myself had articles to harden which could not 
be lapped or ground to their finished' dimensions in 
the turning-lathe owing to their peculiar shapes, so 
that the workman has been compelled to adopt the 
slow process of lapping with a copper file and emery- 
dust, mixed with oil. I have known those articles 
9 



194 EXPANSION AND CONTRACTION OF STEEL. 

which were only once annealed, to take several hours 
to lap them to the finished dimensions after they were 
hardened ; and I have known articles of the same 
kind and of precisely the same dimensions (in their 
soft state), made from the same bar of steel and 
heated to the same temperature (as near as the eye 
could judge), and hardened in water of the same 
temperature, which have been annealed three times, 
scarcely requiring to be touched with the copper file 
after they were hardened. As there may be some 
persons who may perhaps require an article to be 
after hardening as near its original size as possible, 
and who may not perhaps be provided with such 
things as buffs, laps, or stones, I presume therefore 
that this hint will not be out of place in makino- 
those acquainted with it. Another hint deserves a 
place. I have found that articles made of steel 
which have been well forged will always keep truer 
and keep their original sizes better in hardening 
and be less liable to break in hardening, than arti- 
cles which are made of the steel in the state it leaves 
the manufacturer ; for instance, if a very long screw- 
tap, or long rimer, etc., be required for any special 
purpose, it will be well to take a piece of steel 
sufficiently large to admit of being forged to the 
required dimensions. If for a long screw-tap or 
rimer, three-quarters of an inch in diameter, seven- 
eighths round-bar steel swaged down at a cherry-red 
heat to three-quarters and a sixteenth will suffice 
(the one-sixteenth is allowed for turning); but if 
the edges of seven-eighths square steel be hammered 
down so as to form eighth squares and then swaged 



EXPANSION AND CONTRACTION OF STEEL. 195 

down to three-quarters and a sixteenth, it will 
prove even better for the purpose than the seven- 
eighths round-bar steel ; it must be obvious that if 
similar methods be adopted with larger articles, 
they will be less liable to break in hardening. 

To make mistakes at times is the common expe- 
rience of all. It may therefore not be out of place 
to say a few words upon such pieces* of iron-work 
as the mechanic may have the misfortune, through 
some oversight or other, to bore too large, and 
which would in some instances cause the work to 
be useless for the purpose for which it was intended 
were it not possible to contract the hole. The hole 
could, in some instances, be set in by heating the 
work at the forge, and then hammering it upon the 
anvil ; but if the shape of the work be such as not 
to admit of being hammered, or if there be not suf- 
ficient metal to allow hammering, or for removing 
the marks caused by hammering, it will be obvious 
that this method cannot be adopted. Because this 
method cannot be adopted, it does not follow that 
this piece of work should be condemmed as use- 
less ; for the hole may be contracted by adopting 
the process of shrinking. 

It must not be understood,' according to the 
usual term shrinking, that the work should be 
heated, in order to expand the metal and widen the 
hole, and then shrunk upon another piece of work 
whose diameter is larger than the diameter of its 
own hole: for by this method it must be obvious 
that the metal cannot return to its original bulk ; 
consequently the hole cannot return to its original 



19G EXPANSION AND CONTRACTION OF STEEL. 

diameter. And were it to be heated, and allowed to 
become cool in the air of its own accord, without 
being shrunk upon another piece of work, it could 
even then only return to its original dimensions ; 
on the contrary, the piece of work will require to 
be uniformly heated to a red heat, and then im- 
mersed in cold water and entirely quenched. This 
method causes a sudden contraction of the metal, 
consequently the hole becomes smaller. If this 
does not sufficiently contract the hole, the operation 
must be repeated. If after the second heating and 
cooling the contraction be then insufficient, it must 
be operated upon a third time. If after the third 
heating- and cooling the whole be not then sufficiently 
contracted, it will be next to useless to repeat the 
operation, as the particles will have become by this 
time in their most condensed state; at least, in the 
most condensed state they are capable of becoming 
by this operation ; and instead of the hole contract- 
ing smaller, it will become oval, likewise wider at 
each end, or, as the term is, bell-mouthed. If it is 
an iron or steel ring or collar which is being oper- 
ated upon, it will be found that even in the first 
heating and cooling it will cause the whole to be, 
in a slight degree, wider at each end than at the 
central part. This is owing to the two ends or 
edges of the ring becoming cool sooner than the 
central part of the ring ; and, while the two ends 
are becoming cool, they are compressing the cen- 
tral part into a denser state. The central part 
of the ring contracting after the two ends have 
become quite cool, causes this unequal contraction. 



EXPANSION AND CONTRACTION OF STEEL. 197 

This unequal contraction might in a measure be 
prevented, if the operator, previous to heating and 
cooling the ring, take the trouble of shrinking a 
narrow collar upon the outside, at each end of the 
ring, and thus cause the ring to cool more uniform- 
ly. Should these methods not have the desired 
effect of sufficiently contracting the hole (either in 
an iron or steel ring), there is another source open, 
simply to heat the ring to a bright-red heat, and 
then immerse it endways and perpendicular, and 
half its depth in the water, leaving the other half to 
cool in the air above the surface of the water. As 
that part of the ring which is below the surface of 
the water becomes cool, it compresses and thickens 
the other part of the ring, and causes the hole at 
this compressed end of the ring to be considerably 
smaller. The ring will require to be reheated, and 
again immersed in- a similar manner, with the ex- 
ception that the ring must be reversed ; that is, the 
edge which was uppermost in the first instance 
must now be the lower edge. This method will 
accomplish what the other methods failed to do. 
This operation may, if found necessary, be repeated 
several times ; but there is a limit even when this 
method is adopted, when the particles will assume 
their most condensed state, and after which it will 
be useless to repeat the operation, as the ring will 
(even though it be made of iron) ultimately give 
way, and the labor will be lost. Ring-gauges which 
have become worn, may generally by these meth- 
ods be contracted sufficiently to allow for grinding 
them to their original sizes. 



CHAPTER Yin. 
CASE-HARDENING OF WROUGHT IRON", 

It has previously been shown that wrought iron 
is nearly pure decarbonized iron, and not possessed 
of the property of hardening. But I will now en- 
deavor to explain a process by which articles made 
of wrought iron may be exteriorly converted into 
steel, and afterward hardened. The process is called 
case-hardening, and is an operation-, much prac- 
tised, and of considerable use ; and in this, as in 
most of the other arts, differences of opinion exist. 
Some pretend to great secrets in the practice of this 
art, using many fanciful ingredients to which they 
attribute their success ; but my object is to explain 
the most simple and common method adopted, and 
that which I have found in my own experience to 
produce the greatest and the most uniform effect. 
Case-hardening is always a superficial conversion 
of iron into steel, and only differs from cementation 
in being carried on for a shorter time ; for it is sel- 
dom necessary to convert the iron into steel more 
than the sixteenth of an inch deep, unless it is for 
certain parts of machinery where great stiffness as 
w r ell as hardness is required. It is not always mere- 
ly foi economy that iron is case-hardened, but for 
a multitude of articles for various purposes it is bet- 



CASE-HARDENING OF WROUGHT HION. 199 

ter than steel : for it lias the hardness and polish of 
steel externally, with a core of soft fibrous iron in 
the centre : for example, if the mandrels of lathes 
were made of the best cast steel sufficiently hard to 
wear well in the collars, they would be liable to 
break by the twistings and sudden checks to which 
they are at times subjected ; but, by uniting a cer- 
tain quantity of steel with iron, either by welding 
or by the process of case-hardening, the danger of 
their breaking is avoided, and probably serious 
accidents avoided also. The prussiate of potash 
renders iron nearly as hard as steel, by simply heat- 
ing the iron to a red heat, and sprinkling the pot- 
ash finely powdered upon it, and then plunging the 
iron into pure cold water ; but the hardness by this 
process is entirely confined to the surface, and for 
those parts of machinery which have to endure a 
large amount of friction, it is like frittering away 
time to case-harden them with the prussiate of pot- 
ash ; but for some kinds of articles not exposed to 
much wear, a sufficient coating of steel may be ob- 
tained by this process. A much greater, and the 
most uniform effect may be produced by a perfectly 
tight box, and animal carbon alone, such as horns, 
hoofs, or leather, just sufficiently burnt to admit 
of being reduced to powder in order that more 
of it may be got into the box with the articles ; 
bones reduced, to dust will answer the purpose 
equally as well. The box intended for the purpose 
of case-hardening should be made of plate iron; 
the plate iron should, not be less than one-eighth 
part of an inch in thickness ; if the box is required 



200 CASE-HARDENING OF WROUGHT IRON. 

to be used frequently, the plate should not be less 
than three-eighths, or one-half inch in thickness, 
otherwise the box will soon be worn out. The size 
and shape of the box must, of course, differ accord- 
ing to the size, shape, and quantity of articles re- 
quiring to be operated upon. As the iron boxes 
must vary in their construction, and in order to 
make this subject as short and plain as possible, let 
us suppose a square iron box to be already made ; 
the box of course must be furnished with an iron 
lid (a plain piece of plate iron, the size and shape 
of the interior of the box), two holes should be 
pierced in the lid for the convenience of drawing 
testing pieces out of the box at any period of the 
process if required. The top of the box may be 
strengthened and prevented from becoming out 
of shape so readily by the heat, by taking a piece 
of iron about three-quarters of an inch square, 
and bending and welding it into the shape of the 
interior of the box ; and after boring several holes 
into it, it must then be riveted to the box at 
about one inch distance from the top ; besides 
strengthening the box, this will answer for the iron 
lid to rest upon, and thus prevent the lid from press- 
ing upon and bending the articles when they are ex- 
panded by the heat. By placing some clay or loam 
between this iron square and the lid it makes a very 
secure joint. Two holes should be pierced in the box 
at opposite sides, just above the lid, for the conve- 
nience for fastening the lid in its proper place (with 
two iron pins), and making the joint the more 



CASE-HAEDENENG OF WROUGHT IKON. 201 

For occasional case-hardening upon a small 
scale, a very good box may be made by welding a 
ping into the end of a piece of wrought-iron pipe, 
and using a loose ping for the opposite end ; the 
loose plug will, of course, require to be fastened into 
its place with an iron pin passing through it and the 
pipe; it will, of course, require to be luted with 
clay or loam ; part of the plug must project out of 
the pipe for the convenience of pulling it out. 

It may happen that the amateur mechanic may 
have a small article that he wishes to case-harden, 
and, perhaps, he has no box suitable for the purpose, 
and, perhaps, he has no convenience for making one. 
In such an instance a box may be formed of loam ; 
it will require to be gradually dried before it is ex- 
posed to a red heat, otherwise it will probably 
crack. 

The articles intended to be case-hardened being 
previously finished, with the exception of polishing, 
must be put into the iron box in alternate layers with 
the animal carbon, commencing on the bottom of 
the box with the carbon to the thickness of about 
three-quarters of an inch ; upon this a layer of the 
articles must be placed, then another layer of carbon, 
about one-third part in thickness of the first will bo 
sufficient ; upon this another layer of the articles 
and carbon, and so on till the box is nearly full, fin- 
ishing with a layer of carbon, about the thickness 
of the first layer, leaving room every way for the 
expansion of the articles by the heat, otherwise they 
will bend each other in the box. 

After the packing of the box is completed, the 



202 CASE-HARDENING OF WROUGHT IRON. 

lid must be put on and the box luted with clay or 
loam, in order to confine the carbon and exclude the 
atmospheric air. The whole must now be placed in 
a suitable furnace or hollow fire. The fire must not 
be urged, as the contents of the box will require to be 
very gradually and uniformly heated to a red heat ; 
the whole will require to be retained at this heat for 
a period answerable to the depth of steel required. 
In half an hour after the contents of the box have 
arrived at the proper uniform temperature, the depth 
of steel will scarcely be the thickness of a sixpence ; 
in an hour about double the depth, and so on till 
the desired depth of steel is acquired. 

It may be asked what means there are to tell 
when the central articles arrive at the proper heat. 
The auswer to this is, a practical man can judge by 
the heat of the fire and the quantity of articles 
being operated upon ; but I am unwilling to refuse 
a place for the information of those who are unac- 
customed to the operation, therefore I have sug- 
gested, in order to prevent the operator from meet- 
ing with any considerable obstacle, that two holes 
be pierced in the lid of the box for the insertion of 
testing pieces, so that at any period of the process a 
testing piece may be withdrawn and examined. If, 
when a testing piece is withdrawn, it be not suffi- 
ciently heated, the heating must be continued a 
little longer ; after a reasonable time another piece 
may be withdrawn. If this second piece is suffi- 
ciently hot, it may then be hardened in pure cold 
water ; it can then be broken with the hammer, 
and the extent of the carbonization ascertained. It 



CASE-HARDENING OF WROUGHT IRON. ^JI] 

must he borne in mind that different kinds of iron 
absorb carbon unequally ; consequently, the testing 
pieces will require to be made of the same kind of 
iron as the articles, otherwise they will afford false 
results. It may be well to state, that the more 
homogeneous the iron the more equally it absorbs 
carbon ; consequently, the less likely it will be to 
alter its figure in hardening than iron which is not 
homogeneous. 

To save breaking or using any of the articles for 
testing pieces, plain pieces of the same kind of iron 
as the articles may be used for the testing pieces. 
The testing pieces will require to be brightened; 
they will require to be placed (at the time of the 
packing of the box) in the central part of the box, 
and placed in such a manner that they may be 
easily pulled out of the box through the holes in 
the lid, either by a piece of iron wire attached to 
them, or the pieces may be made long enough to 
project through the holes in the lid, so that they 
may be gripped with the pliers and withdrawn. 
The holes in the lid must, of course, be luted with 
loam or clay, the same as the other parts of the 
box. 

When the articles are sufficiently converted, the 
box must be drawn from the fire, the lid taken off, 
and the contents immersed in pure cold water, and 
when cold and taken out, they are ready for polish- 
ing. The articles may (in order to prevent them 
from rusting) be dried by riddling them in a sieve 
with some dry sawdust, after which they may bo 
wiped with a greasy cloth. 



201 CASE-HARDENIXG OF WROUGHT IEON. 

If the articles be immersed in oil instead of 
water, they will be much tougher but less hard, 
though sufficiently hard for some purposes. It is 
not absolutely necessary to immerse the articles 
either in water or oil, direct from the box, as it 
will answer equally well (and sometimes be more 
convenient) to allow them to remain in the box 
until they become cool, and then reheat them in an 
open fire, and immerse them separately. When 
the case-hardening is required to terminate at any 
particular part of an article, the part required soft 
may be bound with thin iron-wire, and then cased 
with loam. This will prevent the carbon coming in 
contact with the iron ; consequently it will prevent 
the carbon penetrating the iron, or, in other words, 
it will prevent the iron from absorbing carbon at 
the part where the wire and loam is placed. The 
loam will require to be gradually dried upon the 
article, previous to putting it into the box, other- 
wise it will probably crack. 

Another method is to shrink an . iron ring or 
collar very tight upon the part not requiring to be 
case-hardened ; but this method is not very econom- 
ical, especially when a large quantity of articles 
requires to be similarly treated. It will be obvious 
that to make and fit a separate collar upon each of 
the articles, when a large quantity is required to be 
operated upon at once, would occupy a great 
amount of labor and time, besides a great amount 
of time will have to be expended in taking the 
collars off again ; and as time is money, this would 
become a very expensive method. To spare the 



CASE-HARDENING OF WROUGHT IRON. 205 

trouble of shrinking a collar upon the article, and 
to prevent the operator from meeting with any con- 
siderable difficulty in getting the collar off again, a 
collar with a hole somewhat larger in diameter 
than the article may be used ; the space between 
the collar and the article must be tilled up with 
loam. There is more economy in this method than 
in the method of shrinking a collar upon the article, 
because the collar can be easily taken off aiid put 
aside to be used again ; whereas, when a collar is 
shrunk tight upon the article it has generally to be 
cut asunder before it can be taken off, consequently 
the collar is useless for future use. The collar may 
certainly be got off by expanding it by hammering ; 
but then this will have the tendency to damage the 
article, that is, if it has been previously finished with 
the exception of polishing. If the article, after 
being cemented with the carbon, be immersed in 
the water previous to taking the collar off, the 
collar will become hard, because it has absorbed 
carbon; consequently, it will require to be ground 
upon the grin ding-stone before it can be cut off 
from the article, either by the chisel, or the file, or 
the turning tool. 

In some instances, Avhen the case-hardening is 
required to terminate at any particular part, it will 
be more convenient and more economical to post- 
pone the finishing of the article until after it has 
been cemented with the carbon. 

In order that a few words may be said upon 
this, we will for example take the mandrel of a 
turning-lathe. Let us suppose then that a new 



206 CASE-HARDENING OF WROUGHT IRON. 

case-hardened mandrel is required to be made. 
The iron selected will require to be forged by the 
smith to the proper dimensions, after which, when 
cold, it will require to be turned in the turning- 
lathe ; those parts of the mandrel which will require 
to be case-hardened must be finished (with the ex- 
ception of grinding and polishing) to the proper di- 
mensions ; those parts of the mandrel not requiring 
to be case-hardened must not be finished, in fact, 
it is immaterial whether they be turned or not, 
until after it has been cemented with the carbon. 
If these parts of the mandrel are turned previous to 
cementing it with carbon, they must not be turned 
to the finished dimensions ; but a greater amount 
of metal must be left upon these parts than what is 
required when it is in a finished state. 

The mandrel being ready for case-hardening, it 
must now be put into an iron box with as much ani- 
mal carbon as will completely envelop it. The box, 
of course, will require to be luted with clay or loam, 
the whole must now be placed in a suitable furnace 
or hollow fire and heated in a similar manner as 
other kinds of articles when requiring to be case-hard- 
ened. When the mandrel is sufficiently converted, 
the box must be drawn out of the fire ; the mandrel 
must be allowed to remain in the box until it be- 
comes quite cool, after which it is ready for the turn- 
ing-lathe. The case-hardening can now be made to 
terminate at any particular part of it, by turning 
the superfluous carbonized metal off, after which it 
may be reheated in an open fire and hardened in 
pure cold water. The carbon once added, the hard- 



CASE-HAKDEOTSTG OF WROUGHT IKON. 207 

ness and softness may be reversed backward and 
forward much in the same manner as steel. 

Iron cemented with animal charcoal, however 
skilfully the operation is performed, is never as te- 
nacious as iron cemented with wood charcoal ; con- 
sequently, it is unfit for cutting-tools, as it will not 
take a fine, firm edge, and, were it to pass through 
the process of forging and melting, it is question- 
able, even then, whether it is in the nature of the 
material to produce such an effect. But if case- 
hardened iron has never been tried for certain kinds 
of springs, it would be worthy of a trial. 



CHAPTER IX. 

TOUGHENING OF STEEL IN OIL. 

Hardening and tempering of steel in oil is 
pretty generally known to be no new process, but 
the toughening of large masses of cast steel in oil is, 
however, a new process for guns ; and in the present 
system of manufacturing built-up guns, it is more than 
probable that it becomes necessary to make certain 
parts of them of steel (toughened in oil.) And here 
I must in justice to that gentleman mention, that 
Mr. Anderson was the first, so far as I know, who 
ever attempted to operate upon large masses of cast 
steel, such as are now operated upon for guns. The 
successful results in this case, and the toughness ac- 
quired in the material by the process, deserve to be 
noted, as it is not generally known, and the infor- 
mation may occasionally prove useful to the engi- 
neer. I may state that the rapid extension of rail- 
roads has led to numerous improvements in the 
material for rails ; and, as they require to be of the 
safest and most durable metal, it is quite probable 
that rails made from ingots of mild cast steel will 
in time supersede all other cheaper but less durable 
materials. It will bo readily imagined that, the 
more homogeneous the metal, the better it will be 
for the purpose of railway bars. Cast steel, from 



TOUGHENING OF STEEL IN OIL. 209 

having been in a state of fusion, is more homoge- 
neous than the usual metal ; and, when it is free from 
all other substances, except a very small portion of 
carbon (which is necessary to form mild steel), its 
qualities then render it eminently well adapted for 
railway bars; and I am myself inclined to think 
that, as soon as it can be cheapened (and. I have my 
reasons for believing that it can be cheapened), it 
will be universally adopted, while wrought and cast 
iron for the purpose will become things of the 
past. 

Railway bars require to be not only homogeneous 
in metal but in the temper also ; but it must not be 
understood, according to the usual term temper 
among mechanics, that the bars should undergo the 
regular process of hardening, and then be reduced 
to a blue, or any other color ; on the contrary, it is 
quite reasonable to suppose, from the small amount 
of carbon which steel suitable for railway bars con- 
tains, that the bars can be submitted to no process 
of preparation so suitable as that of heating them 
uniformly in a suitable furnace to a bright red heat, 
and then entirely quenching them in oil, which will 
leave them in the toughest and most uniform state 
that mild steel is capable of receiving. I can speak 
from experience that a bar after undergoing this 
operation will admit of a very great change of form 
without diminution of its cohesive power; and it is 
quite probable, from the greater hardness of the 
steel, that the bars will be less liable to waste by 
the action of the wheels. The bars being uniform 
in temper throughout, it is obvious, when the upper 



210 TOUGHENING OF STEEL IN OIL. 

surface is worn away by the friction of the wheels, 
that the decay will not be more rapid. The bars 
being more elastic, they will be less liable to be 
broken by continual jars and blows, and they will 
probably be less liable to rust by the action of the 
atmosphere. It is quite probable, also, that a less 
weight of metal might be used ; but, owing to so 
many lives and the vast amount of property which 
depend upon the bars, I am unwilling to recommend 
a less weight of metal. For many other purposes, 
however, for which steel is used, I would not hesi- 
tate to recommend a less weight of metal when the 
steel is toughened in oil. I may state that no 
danger need be apprehended of the steel bars be- 
coming cracked by this process (providing they be 
uniformly heated throughout). Any defect, how- 
ever, whether cracks or flaws, which could not be 
detected while the bars were in their unequal state 
of temper, will by. this process be made visible. I 
am inclined to think if the plates belonging to the 
rollers of rag engines were made of mild cast steel, 
and toughened in oil, that they would be more 
suitable than those now in use. 

Should there be some who are more attentive to 
authority than reason, and who inquire by whom a 
process is used rather than what are its merits, I 
assure them that the process of toughening large 
masses of cast steel is daily practised in the Gun 
Factories' department of Her Majesty's Royal Ar- 
senal, Woolwich. In this department, with a very 
ingeniously contrived apparatus, the process of 
toughening large masses of cast steel is performed 



TOUGHENING OF STEEL IN OIL. 211 

in the following manner : — A block, or tube, of 
mild cast steel (or steel containing a smaller propor- 
tion of carbon than ordinary cast steel) is lifted by 
a powerful crane and placed in a perpendicular po- 
sition in an upright furnace ; an iron coil about six 
inches in depth and about one inch larger in di- 
ameter than the diameter of the block of steel, is 
placed upon the fire bars, at the bottom of the fur- 
nace, for the block of steel to rest upon; beneath 
this iron coil is placed a piece of plate-iron to pro- 
vent the cold air as it passes through the bars com- 
ing in contact with the extreme end of the block 
of steel, and in order to obtain an uniform tempera- 
ture at the extreme end of the block of steel this iron 
coil is filled with wood ashes. The iron coil becomes 
filled with the wood ashes while heating the furnace 
to a red heat with refuse wood previous to putting 
the steel in the furnace. After the block of steel 
is placed in the furnace, the bottom end of it is then 
surrounded with some short blocks of wood ; the 
damper is not lifted until the extreme end has ac- 
quired a low red heat, after which the damper is 
lifted, and the block of steel is then entirely sur- 
rounded with longer pieces of refuse wood, thrown 
in from the top of the furnace. The steel is then 
slowly heated to a bright red heat by the combus- 
tion of the fuel. Wood is used as fuel on account 
of its purity, in preference to coal or coke ; it is not 
so liable to degrade the steel, but lias :i tendency 
to give the steel pliability without diminishing its 
hardness. Just as the steel arrives at a bright red 
heat the vent is closed for a low minutes, in order 



212 TOUGHENING OF STEEL IN OIL. 

to give the steel ample time to soak and so receive 
an uniform temperature throughout the body of the 
steel. For the more uniform the temperature the 
straighter the block will keep, and the steel will ac- 
quire a more uniform temper. I may here state that 
the heat the exterior steel receives is judged of by 
the eye, but the knowledge of the heat of the inte- 
rior steel is only acquired by study, by attention, 
and practice. 

After the steel has acquired the proper uniform 
temperature throughout, the travelling crane is then 
brought over the furnace, the cover belonging to 
the top of the furnace is then removed, after which 
a pair of large iron tongs attached to the crane 
fasten themselves at the top end of the steel block 
or tube. The tongs are so constructed that the 
heavier the weight the tighter they grip the steel; 
still it is found necessary to turn a small collar 
upon the end of the block to prevent the tongs slip- 
ping by the weight. After the tongs have fastened 
themselves upon the block of steel, it is then drawn 
out of the furnace and sunk into a large iron tank 
about twenty feet deep, containing several hundred 
gallons of oil. The heated steel in passing into the 
oil will sometimes cause the surface oil to take fire, 
which, after the whole body of the steel is beneath 
the surface of the oil, is then extinguished by clos- 
ing the covers at the top of the tank and subse- 
quently covering the covers with a piece of canvas. 
The tank has a water space which surrounds the 
oil — the use of the water being to cool the oil. 
The best way to describe the tank is to state that 



TOUGHENING OF STEEL EST OIL. 213 

it is an old steam-boiler sunk endways and perpen- 
dicular in the ground. 

The steel in parting with its heat raises the tem- 
perature of the oil, and, consequently, raises the 
temperature of the water. The water as it becomes 
heated is drawn off at the top by an escape pipe, 
and a supply of cold water is continually running in 
at the bottom. This gentle stream of water run- 
ning through the tank causes the heat to be gradu- 
ally taken from the mass, and the whole cools uni- 
formly in about twelve hours, and exceeding tough- 
ness is the result of the operation ; while it is thus 
made much hio-her in tensile strength, offerin£>' a 
much greater resistance to compression. It is also 
harder and more elastic, and requires a much greater 
force to break it with the hammer ; and it is not worn 
or indented so readily as when received from the tilt, 
or annealed. This operation has in many respects 
the character of annealing, yet it is something mori • ; 
for it is quite certain that a different change of the 
particles takes place, as it leaves the steel in an inter, 
mediate state between hard and soft ; and when mild 
cast steel is required in this particular state, it can 
only be accomplished by a slow process of cooling in 
oil, or some other liquid of the conducting quality 
and which requires as high a temperature to convert 
it into vapor. Steel containing much carbon, oil will 
harden the surface very much more than its internal 
parts, so that it will resist the file; but beneath the 
surface it will be quite soft. In steel containing ;i 
less proportion of carbon there appears i<> l>e very 
little difference between its external and it • internal 



214 TOUGHENING OF STEEL EST OIL. 

parts. In theory there cannot be much difference 
between the external and the internal parts of steel 
containing such a small amount of carbon, and not 
possessed of hardening properties, or only in a slight 
degree ; and in practice, the theory is proved to be 
correct. 

I may here state that the solidity and strength 
of all substances is supposed to depend upon the 
strength of the attraction of cohesion between their 
particles ; because the stronger this is, the more it 
opposes the disunity of the body ; consequently, the 
attraction of cohesion between the particles, after 
the steel has passed through this process, must be 
stronger, on account of its offering a greater resist- 
ance to separation. It must not be imagined that 
the oil penetrates into the pores of the steel, and 
causes it to be more tough ; because, if it were pos- 
sible for the oil to enter the pores, it would then 
lessen the strength of the attraction of cohesion be- 
tween the particles, and the tenacity of the steel 
would be in a measure destroyed. The effect is not 
in the least owing to the penetrating quality of the 
oil ; but the effect is owing to its imperfectly con- 
ducting quality, which causes the steel to part with 
its heat so slowly, and the elevated temperature it 
demands to be converted into the vaporous state. 
A covering of coal is also formed round the steel by 
the burned oil, which greatly retards the transmis- 
sion of heat. This slow rate of cooling is necessa- 
ry to favor a uniform degree of contraction, and 
give the steel a much longer time for the rearrange- 
ment of its particles, and to make the strain more 



TOUGHENING OF STEEL IN OIL. 215 

uniform throughout the body of the steel. Mild 
cast steel, after it has been toughened in oil, may, 
with well-tempered, tools, be turned, bored, planed, 
slotted, chipped, or filed with pleasure. 

If cylindrical or spherical mild-steel shot could 
be toughened, in oil without causing fracture, a 
more effective shot would be the result ; but, owing 
to the thickness and. bulk of shot, it is more than 
probable that an internal fracture would, occur by 
the contraction in cooling. A cylindrical-shaped 
shot made of mild cast steel may, however, be 
toughened in oil without causing fracture, if it be 
first forged or turned nearly to the required finished 
dimensions, and then a hole made in the centre in 
the direction of its length ; the hole need not be 
made completely through, but four inches (more or 
less) at one end of the shot may be left solid: this 
will form a kind of tube with one solid end ; the 
solid end will probably be the best for the rear end 
of the shot. After the hole is made in the shot, 
and it toughened in oil, and subsequently turned 
to the required finished dimensions, the hole may 
then be completely plugged up with a plug made of 
highly carbonized tenacious cast steel. Previous to 
putting the plug in its place, it may be heated to a 
red. heat, and quenched in oil ; or, it may be 
quenched in water and used in its then hard state, 
but it will probably be better to reduce the hard- 
ness of it to a brown or blue temper. The shot 
may be slightly heated in hot oil, or by any other 
suitable means, in order slightly to expand (he 
hole for shrinking the shot upon the plug; or, the 



216 TOUGHENING OF STEEL EST OIL. 

plug may be forced into the hole by hydraulic pres- 
sure without heating the shot ; or, it may be fast- 
ened in by running a small portion of lead round 
it. It will be well, perhaps, to form a shoulder 
upon the plug, so that it may take a bearing on 
some other part of the shot, as well as at the bottom 
of the hole. The front end of this hard ping may 
be level with the front end of the shot, but experi- 
ments may prove it to be better to allow it to pro- 
ject a short distance beyond the end. This hard 
core will offer great resistance to compression, and 
will probably prevent the shot being flattened so 
readily by the blow ; and tempered steel being more 
elastic than untempered steel, or wrought or cast 
iron, it will transmit more faithfully the impulse it 
receives, and the shot will probably prove a more 
destructive weapon than a cast-steel solid shot in its 
soft state, for piercing iron or steel clad ships. Ex- 
periments may perhaps prove the shot to be the 
better by having two or more of these tempered 
plugs let into it. The toughened shot may per- 
haps answer well if the hole were filled up by pour- 
ing molten cast iron into it, the shot of course to 
stand in water while the metal is being poured in 
the hole; the shot will chill the cast iron, and the 
water will prevent the toughness being taken out 
of the shot by the heat of the molten metal. It is 
quite probable also, that a very destructive shot 
may be made by coiling a rod or bar of iron round 
one, two, or more pieces of highly carbonized cast 
or shear bar steel ; then to enclose the whole in an 
iron or steel cylindrical case (the case to have a solid 



TOUGHENING OF STEEL EST OIL. 217 

bottom) ; then to braze the whole into a solid mass, 
with spelter composed of three parts copper and one 
of zinc, or with a more fusible kind of spelter if ne- 
cessary ; when cooled down to the proper tempera- 
ture- to quench the mass in oil or pure water, or 
water with a film of oil upon its surface : it would 
also be worthy of a trial in its soft state. It may 
be well perhaps to explain another plan ; it is this; 
to harden oue, two, or more pieces of bar steel, then 
to brighten and immerse them in solder, which 
melts at a temperature suitable to coat their sur- 
faces with the solder, at the same time rendering 
the steel more tenacious by reducing the hard- 
ness. 

After the pieces have been coated with the 
solder and become cool, then shrink one, two, or 
more iron or steel rings, in a soft or tempered state, 
upon them, the surfaces of the rings to be coated 
with solder in a similar manner as the pieces of bar- 
steel are coated ; then to enclose the whole in an 
iron or steel cylindrical case, and subsequently 
solder the whole into a solid mass, with solder of 
suitable fusibility, to suit the temper of the steel. 

It is quite probable that a very destructive shot 

may be made either by welding a series of rings 

upon one, two, or more pieces of blister or shear 

bar steel, or by coiling a bar of iron round one. 

two, or more pieces of steel, then welding the whole 

into a solid mass; or, if this order were reversed, 

iron inside and steel outside, it might probably 

prove a very destructive shot: but it is obvious 

that there would be greater difficulty in weldii 
10 



218 TOUGHENING OF STEEL LN OIL. 

the mass. The steel may, however, in this instance 
be protected from the direct action of the fire by 
coiling a thin bar of iron upon it ; then to heat and 
place the whole into a strong die, and weld it into 
a solid mass, and subsequently turning the outer 
coil of iron off again. 

It may perhaps be asked by those who are not 
practically acquainted with the hardening and 
tempering of steel, if it would not be better to 
make a solid shot entirely of highly carbonized 
blister, shear, or cast steel, and subsequently harden 
and temper it. The answer is, thick lumps of 
highly carbonized steel, whether hardened in oil 
or pure water, or water with a film of oil upon its 
surface, cannot be hardened without becoming frac- 
tured either internally or externally. It must be 
obvious, then, that the shot would be less effective 
in piercing iron or steel-clad structures than when 
in a soft state. 

Returning to the railway bars, I would state 
that I am myself inclined to think that railway 
bars, either of iron or mild steel, may be made 
more durable, without lessening their safety, by 
heating them uniformly in a suitable furnace to a 
bright red heat, and then immersing their tops or 
heads into some molten highly carbonized cast 
iron, and after keeping them in the molten metal 
for a few minutes, or for a suitable time, which 
could be ascertained by experiment, to quench 
them in oil. By this process the metal will proba- 
bly absorb carbon ; consequently, it will then ac- 
quire a greater degree of hardness, and it is quite 



TOUGHENING OF STEEL IN OIL. 219 

probable that their greater durability would more 
than compensate for the expense of the proa 

It would not be impracticable to case-harden 
the heads of the iron bars by cementing the heads 
in animal charcoal, and then quenching them in 
oil; but.it is questionable whether their greater 
durability would compensate for the expense of 
this process. The bars would be made more dur- 
able as regards wear by cooling them in water; 
but cooling them in water would lessen their safety, 
unless they were made of very pure iron. 



CONCLUSION. 

Befoke I close these details, I wish, to offer a 
few sentiments to the consideration of the young 
artist interested in them, whether he is one who is 
anxious to excel in these particular branches of art, 
as affording the means of honorable livelihood, or 
claims merely the appellation of an amateur, who 
studies mechanical operations from the love of knowl- 
edge, the desire of amusement, or the hope of celeb- 
rity in making discoveries or improvements. Let 
him not be discouraged by the failure of first at- 
tempts ; instead of losing his time in uselessly re- 
gretting his disappointment, let him examine into 
the cause of it, and promptly repeat his experi- 
ments with more precaution. It is a mistaken idea 
that success is absolutely dependent upon length of 
practice, uncommon are the cases in which it fails 
to be the early reward of those who persevere ; the 
reward will always be in proportion to the amount 
of perseverance and ingenuity displayed ; there are 
always difficulties to contend with for the young be- 
ginner. But in every branch of art, if one source of 
experiment fail, there is abundance of other sources 
still open. Further practical directions might easi- 
ly be multiplied, but the necessity for much further 
minuteness of detail upon most of the processes will 



CONCLUSION. 221 

be removed by a little observation, experience, and 
perseverance. But those who postpone perseverance, 
by satisfying themselves with the hope that length 
of practice will perfect them, will in the end regret 
their delusion, and may ineffectually try to •"recover 
their loss, when habitual languor, and other injuri- 
ous habits, have rendered the mind averse to observe, 
and the hand unable to perform. 



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vols, in case. 
Library for my Young Countrymen. 

9 vols, in case. 
Libro Primario de Ortografia. 
Liebig's Laws of Husbandry. 
Life of Man Symbolized by the 

Months of the Year. 
Light and Darkness 
Lights and Shadows of New York 

Picture Galleries. 
Lindsay's Poems. 
Linn's Life and Services. 
Little Builder. 
Little Engineer. 
Livy, with English Note9. 
Logan's Chateau Frissac. 
Looking Glass for the Mind. 
Lord's Poems. 

Christ in Hades: a Poem. 

Louise. 

Lunt's Origin of the Late War. 

Lyell's Elements of Geology. 



Lyell's Principles of Geology. 
Lyra Americana. 
Lyra Anglicana. 

Macaulay's Essays. 1 vol. 

Essays. 1 vols. 

Essays. A New and Revised Edi 

tion, on tinted paper. 6 vols. 
Mackintosh's (Sir James) Essays. 
Madge. 
Mahan's Answer to Colenso. 

Numerals of Scripture. 

Mahon's England. 2 vols. 
Maiu's Novum Testamentum Grrece. 
Mandeville's New Series of Readers. 
1. Primary Reader. 
Second Reader. 
Third Reader. 
Fourth Reader. 
Fifth Reader. 
Mandeville's Course of Reading. 
Reading and Oratory. 
First Spanish Reader. 
Second Spanish Reader. 
Third Spanish Reader. 



2. 
3. 

4. 
5. 



Magnall's Historical Questions. 
Man's Cry and God's Gracious Answer. 
Manners' At Home and Abroad. 
Sedgemoor. 



Manning's Temporal Mission of tho 
Holy Ghost. 
The Reunion of Christendom. 



Manual of Matrimony. 
Markham's History of England. 
Marrayat's Africa. 

Masterman Ready. 

Popular Novels. 12 vols. 

A New and Revised Edition, 

printed on tinted paper 12 
vols. 
Marryat's Settlers in Canada. 
Marshall's (E. 0.) Book of Oratory. 
First Book of Oratory. 



Marshall's (T. W.) Notes on Episco- 
pacy. 

Marsh's Double Entrv Book-keeping. 

Single Entry Book-keeping. 

Bank Book-keeping. 

Book-keeping (in Spanish). 

Blank Books for Double Entry. 

6 books in set. 

Do. for Single Entry. 

set. 

Martha's Hooks and Eyes. 

Martineau's Crofton Boys. 
Peasant and Prince. 



6 books in 



Mary Lee. 

Mary Staunton. 

Mathews on Whist. 

Mayhew's Illustrated Horse Doctor. 

May's Bertram Noel. 

Louis' School Days. 

Mortimer's College Life. 

Sunshine of Greystone. 

McCormick's Visit to Sebastopol. 



